Barbarians brutal critical

[Sandeman]

"Brutal Critical
Beginning at 9th level, you can roll one additional weapon damage die when determining the extra damage for a critical hit with a melee attack."

Does this increase greatsword damage to 3D6 or 4D6?

[PhoenixPhyre]

"Brutal Critical
Beginning at 9th level, you can roll one additional weapon damage die when determining the extra damage for a critical hit with a melee attack."

Does this increase greatsword damage to 3D6 or 4D6?

3d6. Which is why it kinda sucks. Better with a greataxe.

[Sandeman]

Thanks.
I thought so but we had an argument sometime earlier so I wanted to check with others.

[AvatarVecna]

5d6 - hit is 2d6, normal crit is 4d6, brutal critical 1 is 5d6.

All things being equal, greatsword is better until you get brutal critical 2 at lvl 13. Your greataxe crits doing 3d12 will be better than your greatsword crits dealing 5d6, but your greatsword doing 2d6 on hits is better than your greataxe doing 1d12 on hits.

Assuming you hit when you roll 8+ on the die, and assuming advantage from Reckless Attack, barbarian misses 49/400 attacks, hits 312/400 attacks, and crits 39/400 attacks. Assuming the builds are otherwise identical, the only difference is the base weapon damage on hit and crit.

Here's the damage totals/averages over 400 attacks:

No Brutal Critical
312 x 2d6 = 624d6
39 x 4d6 = 156d6

Greatsword: 780d6 (avg 2730)

312 x 1d12 = 312d12
39 x 2d12 = 78d12

Greataxe: 390d12 (avg 2535)

Brutal Critical 1
312 x 2d6 = 624d6
39 x 5d6 = 195d6

Greatsword: 819d6 (avg 2866.5)

312 x 1d12 = 312d12
39 x 3d12 = 117d12

Greataxe: 429d12 (avg 2788.5)

Brutal Critical 2
312 x 2d6 = 624d6
39 x 6d6 = 234d6

Greatsword: 858d6 (avg 3003)

312 x 1d12 = 312d12
39 x 4d12 = 156d12

Greataxe: 468d12 (avg 3042)

Brutal Critical 3
312 x 2d6 = 624d6
39 x 7d6 = 273d6

Greatsword: 897d6 (avg 3193.5)

312 x 1d12 = 312d12
39 x 5d12 = 195d12

Greataxe: 507d12 (avg 3295.5)

Results:
BC0: Greataxe base damage is ~92.86% of Greatsword base damage
BC1: Greataxe base is ~97.28% of Greatsword base damage
BC2: Greataxe base is ~101.3% of Greatsword base damage
BC3: Greataxe base is ~103.94% of Greatsword base damage

[MutantDragon]

What others have said is correct, which is why I think brutal critical should just get reworked in 5.5 to be Xd12 no matter what weapon you use. That way you won't be tied to great axes for the off chance you'll eventually crit. Plus, other martial classes could get an Xd6 version without stepping on the barbarian's toes. Anyway, I'm way off topic at this point. As mentioned above, as the rules are now, with your greatsword example, it'd just give an extra d6.

[PhantomSoul]

5d6 - hit is 2d6, normal crit is 4d6, brutal critical 1 is 5d6.

All things being equal, greatsword is better until you get brutal critical 2 at lvl 13. Your greataxe crits doing 3d12 will be better than your greatsword crits dealing 5d6, but your greatsword doing 2d6 on hits is better than your greataxe doing 1d12 on hits.

Assuming you hit when you roll 8+ on the die, and assuming advantage from Reckless Attack, barbarian misses 49/400 attacks, hits 312/400 attacks, and crits 39/400 attacks. Assuming the builds are otherwise identical, the only difference is the base weapon damage on hit and crit.

Here's the damage totals/averages over 400 attacks:

No Brutal Critical
312 x 2d6 = 624d6
39 x 4d6 = 156d6

Greatsword: 780d6 (avg 2730)

312 x 1d12 = 312d12
39 x 2d12 = 78d12

Greataxe: 390d12 (avg 2535)

Brutal Critical 1
312 x 2d6 = 624d6
39 x 5d6 = 195d6

Greatsword: 819d6 (avg 2866.5)

312 x 1d12 = 312d12
39 x 3d12 = 117d12

Greataxe: 429d12 (avg 2788.5)

Brutal Critical 2
312 x 2d6 = 624d6
39 x 6d6 = 234d6

Greatsword: 858d6 (avg 3003)

312 x 1d12 = 312d12
39 x 4d12 = 156d12

Greataxe: 468d12 (avg 3042)

Brutal Critical 3
312 x 2d6 = 624d6
39 x 7d6 = 273d6

Greatsword: 897d6 (avg 3193.5)

312 x 1d12 = 312d12
39 x 5d12 = 195d12

Greataxe: 507d12 (avg 3295.5)

Results:
BC0: Greataxe base damage is ~92.86% of Greatsword base damage
BC1: Greataxe base is ~97.28% of Greatsword base damage
BC2: Greataxe base is ~101.3% of Greatsword base damage
BC3: Greataxe base is ~103.94% of Greatsword base damage

To give some anydice (https://anydice.com/) ability to run numbers easily (assuming I haven't messed this up! :) ),



\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
\ Function: simulate \
\ Simulates damage based on the \
\ attack roll, the roll of on \
\ the die required to hit, and \
\ damage parameters. \
\ X = attack roll die \
\ Y = required roll to hit \
\ A = baseline weapon damage \
\ B = bonus damage on every hit \
\ C = bonus damage on a crit \
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
function: X:n Y A B C simulate {
if X = 20 {result: A + A + B + C}
if X < Y {result: 0}
result: A + B
}


so inputting this



\\\\\\\\\\\\\\
\Actual rolls\
\\\\\\\\\\\\\\
output [d20 10 2d6 8 1d6 simulate] named "Greatsword, needs 10+, Brb 9"
output [d20 10 1d12 8 1d12 simulate] named "Greataxe, needs 10+, Brb 9"
output [d20 10 2d6 8 2d6 simulate] named "Greatsword, needs 10+, Brb 13"
output [d20 10 1d12 8 2d12 simulate] named "Greataxe, needs 10+, Brb 13"
output [d20 10 2d6 9 3d6 simulate] named "Greatsword, needs 10+, Brb 17"
output [d20 10 1d12 9 3d12 simulate] named "Greataxe, needs 10+, Brb 17"


into anydice afterwards computes the damage comparison from:
(a) A raging barbarian (not using reckless attack) with +5 strength wielding a Greatsword at level 9 (so Brutal Critical 1 giving +1d6, rage giving +3)
(a) A raging barbarian (not using reckless attack) with +5 strength wielding a Greataxe at level 9 (so Brutal Critical 1 giving +1d12, rage giving +3)
(a) A raging barbarian (not using reckless attack) with +5 strength wielding a Greatsword at level 13 (so Brutal Critical 2 giving +2d6, rage giving +3)
(a) A raging barbarian (not using reckless attack) with +5 strength wielding a Greataxe at level 13 (so Brutal Critical 2 giving +2d12, rage giving +3)
(a) A raging barbarian (not using reckless attack) with +5 strength wielding a Greatsword at level 17 (so Brutal Critical 3 giving +3d6, rage giving +4)
(a) A raging barbarian (not using reckless attack) with +5 strength wielding a Greataxe at level 17 (so Brutal Critical 3 giving +3d12, rage giving +4)
In all cases for simplicity (tweak as desired), a value of 10 on the d20 for your attack roll is needed to hit. It's easier to view comparisons if you compare pairs of the same level, removing others.

The link to this exact calculation: https://anydice.com/program/2b715

(In practice for the damage roll components, A is anything you'd double up on on a crit; B is anything you don't double up on on a crit, and C is anything you only get to roll on a crit.)

[Schwann145]

It's a ridiculous position based entirely on a specific reading of a poorly worded ability. Greatswords don't have "a die" value; their value is 2d6, not d6.
This is an area where 4e D&D is just superior.

My suggestion? Do it like 4e did. Treat "2d6" as [W] (weapon damage), and add it again as appropriate.

To be clear, the official rule is as mentioned above. IMO, the official rule is stupid. :smallyuk:

[PhantomSoul]

To be clear, the official rule is as mentioned above. IMO, the official rule is stupid. :smallyuk:

Yeah, in a better-developed system a single-die interpretation could be interesting... but 5e goes out of its way to be as dull as possible for the weapon system, so it really does seem in keeping with the system to just treat it as 2d6 so that Greataxes and Greatswords are more directly comparable. Most tables I've seen just treat 2d6 as the die for Barbarians for this.

[Zhorn]

Looks like I'll be bucking the trend of this thread and say I actually like that Brutal critical is giving Greatswords just one extra d6
Greatswords doing better damage on average than a Greataxe makes this an area where the Greataxe gets back a perk of it's own so the Greatsword isn't winning out between the two on ALL scenarios.
It's a minor difference, but it is still a difference the player can make an actual choice on.

Want more reliable damage on your normal hits? Greatsword

Want crits to feel more impactful? Greataxe

not a fan of suggestions that just equate to all things being the same all the time

[Keltest]

Looks like I'll be bucking the trend of this thread and say I actually like that Brutal critical is giving Greatswords just one extra d6
Greatswords doing better damage on average than a Greataxe makes this an area where the Greataxe gets back a perk of it's own so the Greatsword isn't winning out between the two on ALL scenarios.
It's a minor difference, but it is still a difference the player can make an actual choice on.

Want more reliable damage on your normal hits? Greatsword

Want crits to feel more impactful? Greataxe

not a fan of suggestions that just equate to all things being the same all the time

Agreed. Let the greataxe have the win.

[PhantomSoul]

Looks like I'll be bucking the trend of this thread and say I actually like that Brutal critical is giving Greatswords just one extra d6
Greatswords doing better damage on average than a Greataxe makes this an area where the Greataxe gets back a perk of it's own so the Greatsword isn't winning out between the two on ALL scenarios.
It's a minor difference, but it is still a difference the player can make an actual choice on.

Want more reliable damage on your normal hits? Greatsword

Want crits to feel more impactful? Greataxe

not a fan of suggestions that just equate to all things being the same all the time

I like there being a difference between weapons (as implied by the grump at 5e's weapons in my post)... I just want it to be more significant than this paltry instance that's quite restricted! :)

[Zhorn]

I like there being a difference between weapons (as implied by the grump at 5e's weapons in my post)... I just want it to be more significant than this paltry instance that's quite restricted! :)
That's part of the catch; make the differences TOO significant and you'll circle back to one specific weapon being the best allrounder in all scenarios again, or requiring a numbers bloat to make the less occurring instance be worth while.
There is a point in design where you need to hold back and stick to a smaller scope as to avoid runaway conditions and wild overcorrections.

Brutal Critical is one of those areas where I think they did it right. It mechanically encourages the iconic 'Barbarian with a Greataxe' trope, while not being so out and away superior that choosing to go with a Greatsword or Glaive isn't also viable.

[Segev]

Looks like I'll be bucking the trend of this thread and say I actually like that Brutal critical is giving Greatswords just one extra d6
Greatswords doing better damage on average than a Greataxe makes this an area where the Greataxe gets back a perk of it's own so the Greatsword isn't winning out between the two on ALL scenarios.
It's a minor difference, but it is still a difference the player can make an actual choice on.

Want more reliable damage on your normal hits? Greatsword

Want crits to feel more impactful? Greataxe

not a fan of suggestions that just equate to all things being the same all the time

Seconding the sentiment and adding my own thoughts: I think thus was deliberate. Barbarians iconically wield greataxes, which are iconically d12 weapons (Barbarians are oft said to be the d12 class, in fact.)

Making brutal critical reward having one larger die over two smaller ones encourages, but doesn't force, greataxes over greatswords.

[Sandeman]

My table agreed earlier to let all greatweapons be either 1d12 or 2d6 by player choice.
So your choice of weapon (sword, maul, axe) was just cosmetic except for damage type (slashing, bludgeoning).
And I think we will treat the Brutal critical feature as just doubling the weapon dice to make it easy.

[Zhorn]

On the one hand offering the choice between 1d12 or 2d6 for any greataxe/greatsword/maul frees up the thematic choice

But on the other hand; combined with making Brutal Critical do +2d6 instead of strictly a single dice makes the greatsword superior all round; Lowest weight
best average damage
best average crits
highest damage floor
Erasing niches where 1d12 was better and encouraging cookie-cutter gearing.

[DarknessEternal]

Erasing niches encouraging cookie-cutter gearing.

And yet, Polearm Master exists.

[Sandeman]

On the one hand offering the choice between 1d12 or 2d6 for any greataxe/greatsword/maul frees up the thematic choice, combined with making Brutal Critical do +2d6 instead of strictly a single dice makes the greatsword superior all round; Lowest weight, best average damage, best average crits, highest damage floor.
Erasing niches encouraging cookie-cutter gearing.

Yes. But for all non-barbarian classes, we find it quite liberating to not having to pick weapon type based on damage stats. Just pick what you think fits best concept wise.
You want to use a greataxe with a fighter (and reroll 1 and 2s from GWF fighting style) while rolling 2d6 for damage? Sure, go ahead.

[Witty Username]

Yes. But for all non-barbatian classes, we find it quite liberating to not having to pick weapon type based on damage stats. Just pick what you think fits best concept wise.
You want to use a greataxe with a fighter (and reroll 1 and 2s from GWF fighting style) while rolling 2d6 for damage? Sure, go ahead.
GWF actually benefits great axe more than greatsword as well.
Averages cover up a quirk of weapons in this case:
Rolling a 1-2 and an 11-12 with a great axe are equally likely as is a 6-7.
Meanwhile rolling a 2 or 12 on 2d6 is much less likely in comparison to a 6 or 7.

Generally speaking, at least heavy weapons are pretty well balanced against each other.

Thematic choices away, also you will find your weapons occasionally lean into your themes in small ways.

Edit: since PAM got brought up. This still holds true a bit, Pam weapons tend to have lower base damage straight out with smaller dice, and pam does cost a feat and the extra feat is a bonus action.
For heavy weapons, PAM is another way to do, but not the only way to do.

[Frogreaver]

GWF actually benefits great axe more than greatsword as well.
Averages cover up a quirk of weapons in this case:
Rolling a 1-2 and an 11-12 with a great axe are equally likely as is a 6-7.
Meanwhile rolling a 2 or 12 on 2d6 is much less likely in comparison to a 6 or 7.

Generally speaking, at least heavy weapons are pretty well balanced against each other.

Thematic choices away, also you will find your weapons occasionally lean into your themes in small ways.

Edit: since PAM got brought up. This still holds true a bit, Pam weapons tend to have lower base damage straight out with smaller dice, and pam does cost a feat and the extra feat is a bonus action.
For heavy weapons, PAM is another way to do, but not the only way to do.

I understand the math. I don’t understand the explanation or your assertion. On average GWF adds more damage to 2d6 than 1d12. It does this by triggering much more often (5/9 vs 1/6).

[Segev]

GWF actually benefits great axe more than greatsword as well.
Averages cover up a quirk of weapons in this case:
Rolling a 1-2 and an 11-12 with a great axe are equally likely as is a 6-7.
Meanwhile rolling a 2 or 12 on 2d6 is much less likely in comparison to a 6 or 7.

Technically, GWF says: "When you roll a 1 or 2 on a damage die for an attack you make with a melee weapon that you are wielding with two hands..."

Not "when you roll a 1 or 2 for damage on the dice," but rather, "when you roll a 1 or 2 on a damage die." This means that I think it actually benefits the greatsword even more, since if you roll a 1 or 2 on either of the d6s, you can reroll that d6.

[Witty Username]

I understand the math. I don’t understand the explanation or your assertion. On average GWF adds more damage to 2d6 than 1d12. It does this by triggering much more often (5/9 vs 1/6).

There is also the concern of reroll.
Rolling a 1-2 on a 1d6 is much more likely than a 1-2 on a 1d12, but the average increase is more complex than that, as a 1-2 rerolled on a d12 is much more likely to roll more than 2. While 1d6 rerolled will still get a 1-2 a fair amount of the time.

This is most obvious with 2d4 (don't remember if double scimitar works with gwf and don't much care) you will proc almost all the time but the actual increase in damage is minimal.

Generally d12 is more likely to get prominent increases and effective rerolls than 2d6, 2d6 is more likely to get rerolls, but also lackluster to poor rerolls and the ceiling of increase is much less.
--
In short, Segev, you right, but there is more too it than that.

[Segev]

In short, Segev, you right, but there is more too it than that.

Indeed. Here's an anydice (https://anydice.com/program/2b783) script to explore it.

[Zhorn]

Yes. But for all non-barbarian classes, we find it quite liberating to not having to pick weapon type based on damage stats. Just pick what you think fits best concept wise.
You want to use a greataxe with a fighter (and reroll 1 and 2s from GWF fighting style) while rolling 2d6 for damage? Sure, go ahead.
Yes, that's what I was saying regarding 'on the one hand'. My bad for not including a 'but' to make a clear delineation between it and the following point.

Flavour is free, and refluffing from a purely cosmetic and thematical standpoint is an action I would encourage more tables to do before resorting to homebrew and houserules.

The second part though, which you admit has no bearing on your table with no barbarians, would only serve to further buff the 2d6 choice to make it constantly superior to the 1d12 weapon option.

The first point IS freeing up thematic choices
The second is making the thematic choice meaningless as 2d6 now an all-round mechanically superior

[Yakk]

Brutal critical is so bad, you shouldn't care.

Really.

The impact from brutal critical on your damage output is so low, just ignore it.

I guess it is fun to up your crit damage.

[Segev]

It's a reason to dip Fighter 3 for Champion, perhaps. ...perhaps.

[RogueJK]

But for all non-barbarian classes, we find it quite liberating to not having to pick weapon type based on damage stats.

Well, there are non-Barbarian examples where it would come into play...

Take the Undead Warlock. Like Brutal Critical, their Grave Touched feature allows you to add a damage dice, making a Greataxe a better option for a melee Undead Warlock than a Greatsword. (And unlike Brutal Critical, you can do this 1x/turn when Form of Dread is active, rather than just on crits.)

Also, Half-Orcs get Savage Attacks, which functions just like Brutal Critical. So even a non-Barbarian Half-Orc might choose to go with a Greataxe over a Greatsword, especially on a crit-fishing build.

Plus the aforementioned greater benefit for the Great Weapon Fighting Style for a Greataxe compared to a Greatsword.


Heck, slap all that together, and you could run a Half Orc Fighter 1/Undead Bladelock X with a Greataxe and GWF style, and really leverage the Greataxe's benefits.


So it's not just Barbarians that would want to consider Greataxe over Greatsword.

[Yakk]

It's a reason to dip Fighter 3 for Champion, perhaps. ...perhaps.
Stop at 5ish, and get Champion ... perhaps. With reckless and GWM on a 60% base hit rate foe, you now have a 58% hit 19% crit rate, doing 1d12*.77 + .58*14 = 13.1 instead of 84% hit 19% crit on 1d12*1.03 + .84*4 = 10.1.

Getting Brutal Crit after 19-20 crit range and constant reckless earns you all of 0.19 * 6.5 = 1.235 damage per swing. Gloom 4 meanwhile would get you 16.6 damage per combat (and +13.1 damage per encounter), which is a LOT of swings to catch up with. Brutal Crit doesn't matter all that much, even if you try to optimize around it isn't all that big.

I mean, I've tried.

Crit fishing generating meaningful damage per round in 5e needs lots of Rogue levels, or 2 Paladin and spell slots to fuel it. Nothing else seems to do enough to move the needle; it acts like a ribbon, not a feature.

[AvatarVecna]

Looks like I'll be bucking the trend of this thread and say I actually like that Brutal critical is giving Greatswords just one extra d6
Greatswords doing better damage on average than a Greataxe makes this an area where the Greataxe gets back a perk of it's own so the Greatsword isn't winning out between the two on ALL scenarios.
It's a minor difference, but it is still a difference the player can make an actual choice on.

Want more reliable damage on your normal hits? Greatsword

Want crits to feel more impactful? Greataxe

not a fan of suggestions that just equate to all things being the same all the time

I didn't give an opinion on it, but this is also my opinion. I think giving barbarians more reason to use a greataxe is a good thing.

[Segev]

Stop at 5ish, and get Champion ... perhaps. With reckless and GWM on a 60% base hit rate foe, you now have a 58% hit 19% crit rate, doing 1d12*.77 + .58*14 = 13.1 instead of 84% hit 19% crit on 1d12*1.03 + .84*4 = 10.1.

Getting Brutal Crit after 19-20 crit range and constant reckless earns you all of 0.19 * 6.5 = 1.235 damage per swing. Gloom 4 meanwhile would get you 16.6 damage per combat (and +13.1 damage per encounter), which is a LOT of swings to catch up with. Brutal Crit doesn't matter all that much, even if you try to optimize around it isn't all that big.

I mean, I've tried.

Crit fishing generating meaningful damage per round in 5e needs lots of Rogue levels, or 2 Paladin and spell slots to fuel it. Nothing else seems to do enough to move the needle; it acts like a ribbon, not a feature.

If I were trying to crit-fish as a barbarian, I would go Half-Orc, Barbarian 9 (for brutal critical)/Fighter 3 (take GWF with Fighter and Champion for 19-20 crit), and seriously consider Berserker (though that's really just 1 fight/day that you function in, so it's not very good, unless your party cleric is willing to spend a greater restoration after every fight on you). And go greataxe, of course. But even then, GWF rewards greatsword more than greataxe, and that's more consistent. That said, if you do crit, 4d12 with the ability to reroll 1s and 2s is pretty good, when you get it. Reckless attack and critting on 19-20 certainly feels pretty good.

I'm kind-of tempted to homebrew up a Mantis Totem for the Totem Warrior that, at level 3, gives the 19-20 crit range and, if a crit drops a target to 0, decapitates them (killing them if they can't live without the head being cut off). Build the 19-20 crit range into the Barbarian build directly, at least in one path.

[Yakk]

If I were trying to crit-fish as a barbarian, I would go Half-Orc, Barbarian 9 (for brutal critical)/Fighter 3 (take GWF with Fighter and Champion for 19-20 crit), and seriously consider Berserker (though that's really just 1 fight/day that you function in, so it's not very good, unless your party cleric is willing to spend a greater restoration after every fight on you). And go greataxe, of course. But even then, GWF rewards greatsword more than greataxe, and that's more consistent. That said, if you do crit, 4d12 with the ability to reroll 1s and 2s is pretty good, when you get it. Reckless attack and critting on 19-20 certainly feels pretty good.

I'm kind-of tempted to homebrew up a Mantis Totem for the Totem Warrior that, at level 3, gives the 19-20 crit range and, if a crit drops a target to 0, decapitates them (killing them if they can't live without the head being cut off). Build the 19-20 crit range into the Barbarian build directly, at least in one path.
Sure, so we have +2d12 damage on 19% of swings (over someone who didn't fish). 1/6 * 1d12 + 5/6 * 1d10+2 is That is 14.7 * .19 = 2.8 damage per swing, or 5.6 per action.

That isn't nothing, but it isn't all that big either. And half of it didn't require barbarian 9 at all.

Swap those 4 levels of barbarian and lose 2.8 damage per action. Gain about 18-32 damage per combat from gloomstalker 4 plus a pile of utility.

Even on a crit-fish based build, getting barbarian 9 isn't effective.

[RogueJK]

Crit fishing generating meaningful damage per round in 5e needs lots of Rogue levels, or 2 Paladin and spell slots to fuel it.

There are other ways to generate a pile of additional damage dice for meaningful critical hit novas, besides just Rogue or Paladin.

Stuff like 5+ levels of Bladelock with the Eldritch Smite invocation.

Or potentially something more eclectic like a Level 10+ High Half Elf Whispers Bard, adding in dice from BB/GFB, Psychic Blades quasi-smite, and another damage-boosting Magical Secrets spell like Holy Weapon or Shadow Blade.


Take for example a crit-fishing Elven Undead Bladelock 6/Whispers Bard 5 with a Rapier and the Elven Accuracy feat. You've got Elven Accuracy with multiple methods to generate your own Triple Advantage via spells (if needed), plus Extra Attack, and the ability to add extra damage dice to your 1d8 Rapier from Eldritch Smite (+4d8) plus Grave Touched (+1d8) plus Psychic Blades (+3d6) plus potentially another damage-boosting Concentration spell like Hex (+1d6), all of which is doubled on a crit.

That's 12d8+8d6 on a crit, with nary a Paladin nor Rogue level in sight.

(And your Eldritch Smite slots and Psychic Blades uses both regenerate on a Short Rest.)

[Segev]

So, what would a barbarian nine need in addition to brutal critical to make it worthwhile compared to the multiclass alternatives that leap out at level 6 or 7?

[RogueJK]

So, what would a barbarian nine need in addition to brutal critical to make it worthwhile compared to the multiclass alternatives that leap out at level 6 or 7?

Simply put: Something to add significant extra damage dice, beyond just the lone extra damage dice of Brutal Critical.

You'd need to stack several sources of additional damage dice. Half Orc's Savage Attacks (adding another damage dice) would be the most obvious first step.

From there, you're looking at something like Whispers Bard 3+, Paladin 2/Full Caster X, or Blade Pact Warlock 5+ for Smite or Psychic Blades damage. (But since you can't cast or concentrate on spells while raging, you wouldn't be able to make full use of these spellcasting classes' abilities.)

Or if you're willing to drop down from a Greataxe to a Rapier, Rogue levels for Sneak Attack could be a good option, since Barbarian/Rogue is already a synergistic combo in a number of ways. And could let you take the Piercer feat for yet another added damage dice on a crit.

Something like a Half Orc Barbarian 9/Rogue 11 with the Piercer feat and a Rapier would be doing 5d8+12d6 on a crit. (But even then, I'd rather duck out of Barbarian at 5 or 6, and take the extra 3-4 Rogue levels instead, trading +1d8 Brutal Critical for +2d6/+4d6 added Sneak Attack critical damage.)

[Yakk]

So, what would a barbarian nine need in addition to brutal critical to make it worthwhile compared to the multiclass alternatives that leap out at level 6 or 7?

Adding 19-20 crit range (possibly only while raging) males brutal 9 acceptable; removing the champ 3 tax on it. And making it dice, not die.

For later ones, adding 2 sets of weapon dice instead of 1.

[Segev]

Adding 19-20 crit range (possibly only while raging) males brutal 9 acceptable; removing the champ 3 tax on it. And making it dice, not die.

For later ones, adding 2 sets of weapon dice instead of 1.

I do like it adding dice rather than "die blocks," i.e. greatswords still add only d6s as a way to encourage greataxe barbarians.

I was thinking maybe adding a number of extra dice equal to the rage damage bonus, rather than +1 and later +2. That'd make it +3 and then later +4, instead. Maybe, when it would have gotten the second extra die, change it to "if you have advantage, and the lower die result would have hit, it counts as a critical hit?"

[N810]

I do like it adding dice rather than "die blocks," i.e. greatswords still add only d6s as a way to encourage greataxe barbarians.

I was thinking maybe adding a number of extra dice equal to the rage damage bonus, rather than +1 and later +2. That'd make it +3 and then later +4, instead. Maybe, when it would have gotten the second extra die, change it to "if you have advantage, and the lower die result would have hit, it counts as a critical hit?"

Sounds similar to the UA "Fell handed"' feat.

[CTurbo]

Brutal Critical is a bad feature in general, but it's hilariously bad for a level 9 feature. Level 3 would probably be more appropriate and even then it still wouldn't be great.

I propose something bonkers like at level 9, Brutal Critical straight up doubles damage on a crit, and later on, at level 17, it triples damage on a crit. If that's too crazy, maybe just at level 9, you add your Str mod twice, at level 13, you add your Str mod 3x, and at level 17, you add your Str mod 4x. Maybe even 1 extra weapon damage die AND double/triple/quadruple Str mod.

As far as the Greataxe vs Greatsword debate, I haven't crunched numbers, but GWF and also Savage Attacker FEEL better with a Greataxe than a Greatsword. My buddy played a Half Orc Greataxe wielding Champion with GWF and Savage Attacker and many times he turned a 1 into a 10, 11, or 12. Sure there was an occasion where the 1 got turned into a 3, but for the most part, the d12 reroll made for a pretty substantial gain in damage.

GWF and Savage Attacker are both pretty weak in general, but they definitely feel at their best using a Greataxe IMO.

I do think that Brutal Critical was written deliberately to give the edge to the Greataxe.

[Leon]

If i was going all in on it i'd be playing a Half Orc with a Pike and the piercer feat but really its better to play what you feel is good than what some metrics tell you is "best"