How would you make an evil version of the holy avenger sword?

[Spacehamster]

What stats and bonuses would you give a corrupted holy avenger sword, basically
artifact level weapon for evil fighters and oathbreakers out there. :)

[Beleriphon]

What stats and bonuses would you give a corrupted holy avenger sword, basically
artifact level weapon for evil fighters and oathbreakers out there. :)

The Unholy Revenger, just flip the bonuses to reflect that evil types are stabbing celestials and puppies.

[Spacehamster]

The Unholy Revenger, just flip the bonuses to reflect that evil types are stabbing celestials and puppies.

lol I were thinking more along the lines of more powerful then the holy blade but at a price, so some form of curse and more offensive power instead of defensive. :)

[MaxWilson]

What stats and bonuses would you give a corrupted holy avenger sword, basically
artifact level weapon for evil fighters and oathbreakers out there. :)

Blackrazor, right there in the DMG.

[Axorfett12]

Blackrazor even comes with a drawback.

Barring that, I'd say just use a holy avenger, but give bonuses against fey and Celestial instead of fiend and undead.

[MrUberGr]

So off the top of my head:

a) Aura part. Instead of you and your allies having advantage, it could be something like a frightful presence (Wis save -> frightened etc) OR disadvantage for your enemies.

b) drawback part

Bloodpact. To attune to this weapon, you must make a sacrifice of your own well being. You loose 2xlevel hit points. However, whenever you deal damage you restore 2+Con mod hit points or gain temporary hitpoints if you are max health.

Something along these lines. As I said the numbers are there just to give an example. You can see what's what and fix it.

c) damage part, I think celestials have resistance to necrotic, so you could say, force type to celestials.