You want a single person to cover every role in the party? Ask and ye shall receive.

Everyone Is Here

Artificer 2/Barbarian 1/Bard 1/Cleric 1/Druid 1/Samurai Fighter 6/Monk 1/Paladin 2/Ranger 1/Rogue 1/Sorcerer 1/Warlock 1/Wizard 1
Race: Human
Starting Stats: STR 13, DEX 14, CON 14, INT 13, WIS 13, CHA 14
Background: Folk Hero

1st level: Hi, I'm Jerry Averageguy
Jerry will start off as a Fighter for our first two levels, partially because gaining proficiency in everything combat-related is pretty sweet, but mostly because Action Surge is going to be essential to juggle all of your class features that you're about to get. For now, he's pretty a pretty standard Fighter, who will take the Defense fighting style and a one-handed weapon, since he'll want a hand free to cast spells and whatnot.

3rd level: Obligatory Hexblade Dip
Now Jerry's going to multiclass into a Hexblade Warlock. (Whew. Two down, eleven to go.) The more SAD he is, the better, and he really can't be the face of the party without decent Charisma anyways. Lightning Lure, Booming Blade, Hellish Rebuke and Hex will be his only spells for a while, but these are all pretty useful in combat, so no harm done (to him. Maybe to the other guy). Jerry will now take four more levels in Fighter; he's picking up the Samurai subclass for the at-will advantage, two ASIs to pump Charisma to 18, and Extra Attack.

Now Jerry is a 7th level Charisma-based Fighter with 17 AC and some smackin' spells. Not a bad start. But a little too focused on combat, don't you think?

8th level: Branching Out
At this point, Jerry's reached a decent amount of combat effectiveness, and his healing needs can be met by Second Wind for the short term. In other words, it's a good breakpoint. So now we want to start to have some utility options. Might as well bite the bullet now, while Jerry still mostly has d10 hit dice: take a level in Ranger. Hopefully by this point we've gotten some idea as to what types of enemies Jerry is facing and what terrain he's primarily in. Oh, and he get a free skill, too.

In the grand tradition of 9th level being a dead level for most classes, we'll have Jerry take his level of Monk now.

Next, we want Jerry to go Wizard, but since his Intelligence is nothing special, let's not rely on it; choose Feather Fall, Expeditious Retreat, Find Familiar, Identify, Comprehend Languages, and Unseen Servant for Jerry's spellbook. He'll prepare Feather Fall and Expeditious Retreat, and never touch the others unless he's ritual casting them. Light, Prestidigitation, and Mage Hand will be his cantrips.

From there, Jerry will pop into a level of Bard and grumble at how useless Bardic Inspiration is, accept his free skill and musical instrument proficiencies with grace, and take keen interest in the spells that he's just chosen: Minor Illusion and Thunderclap for his cantrips, and Bane, Charm Person, Distort Value, and Dissonant Whispers as his proper 1st-level spells. These all require saving throws of some sort, but wouldn't you know it - Jerry had the foresight to pump his Charisma super-high!

But since he's on a roll here, let's snap up a level of Sorcerer. It would be a shame to waste that Charisma score, so for our spells, let's go Chill Touch, Firebolt, Frostbite, and Ray of Frost. And Absorb Elements and Shield. And his Sorcerous Origin will be Wild Magic, because Tides of Chaos is fun and he will get a lot of mileage out of it with his chosen spells.

Ten spells, nine cantrips, six spell slots, and five classes later, I'd say Jerry has a fair bit of utility.

13th level: Still Standing Strong
13th level is another traditional dead level, so we'll pick up our Barbarian dip here.

At 14th level, Jerry's healing is probably falling behind a little bit, since he's been relying on Second Wind this whole time. Let's remedy that by dipping our toes into the Life Cleric domain, and right away all of his healing spells restore an additional 3hp to himself. What healing spells, you ask? Well, the ones he just got as a cleric. To be more specific, Jerry will have four cleric spells prepared each day: Cure Wounds and Bless are non-negotiable, and we want Healing Word and Detect Magic, since they're more healing and a ritual, respectively. And since he gets three cantrips, let's snag Guidance, Mending, and Thaumaturgy.

But it doesn't end here. I'm sure we're all aware of the Goodberry/Life Cleric cheese, and what better way to grab Goodberry than by taking a level of Druid? (The other spell he can prepare doesn't matter much.). That's a total of 30hp per casting. For cantrips, let's have Jerry pick up Mold Earth, Shape Water, and Druidcraft. Also, since it should've become clear by now that his Wisdom score is a lie, we'll just ignore the whole "can't use metal" shtick.

For those keeping track, Jerry now has 16 1st-level spells, 15 cantrips, 9 spell slots, 8 classes, and ~380 potential heals from Goodberry and Second Wind.

16th level: Picking Up Slack
Jerry left his ASIs behind a long, long time ago, and it may be starting to show by now. So he'll cheat a little bit. He'll take two levels of Artificer, and nab the Enhanced Defense and Enhanced Weapon infusions. While you're there, see if you can craft yourself a keyring or something for all your arcane focuses and holy symbols and whatnot, because I can't imagine juggling them is very easy. He gets two cantrips and can prepare one spell, so he'll grab Dancing Lights, Spare the Dying, and prepare...I don't know, Alarm? Jerry's almost run out of 1st-level spells to take, and at least this one's a ritual.

A level in Rogue isn't bad, since Jerry gets a skill and Expertise. And Thieves' Cant, but nobody cares about that.

But the saving grace is the Paladin. This two-level dip is Jerry's capstone, and it kinda delivers. Lay on Hands is an extra 10hp, and he'll want the Defense fighting style. However, Jerry has suddenly come into a wealth of damage: Divine Smite. And coincidentally, the highest level spell slot he has is also the highest slot he can convert into a Smite without wasting anything. So his damage output just increased by several d8 a turn.

20th level: The Good, the Bad, and the Ugly Character Sheet
In my mind, I've separated classes into four roles: Tank, Utility, Support, and the Face. A tank is the guy who's good in combat and won't die easily. Utility is the person who provides out-of-combat stuff like exploration and skill checks. Support gives in-combat buffs and healing. And the Face is the guy who can talk to shopkeepers without having the town guard called down on him.

So how does Jerry Averageguy fill all of these roles? Well, he's a 6th-level fighter with two attacks, 19 AC, Divine Smite and all the spell slots to back it up, so he can wade into a group of enemies, not die instantly, and still probably come out on top. I'd say that's a tank, all right. With his 18 Charisma, he's a decent party face. He's got a plethora of 1st-level spells and extra skills to provide utility and support. And he has enough healing to keep himself from dying.

Can Jerry do any of these effectively? Well, no. Not at all. He was never intended to. Conceptually, this is probably the simplest build in the thread; he's the purest essence of multiclassing distilled into a single character. In fact, when the PHB describes multiclassing, it gives us this little gem: "Compared to a single-class character of the same level, you'll sacrifice some focus in exchange for versatility" and I have never seen a truer statement.

Incidentally, this build only has the same number of spell slots as a 1/3 caster like the Eldritch Knight.

Spoiler: Snapshots:
Show
Y'know, the 5/11/17/20 snapshots really aren't the best way for displaying a build like this.

5th level:
Fighter 2/Hexblade 1/Samurai Fighter 2
Stats: STR 13, DEX 14, CON 14, INT 13, WIS 13, CHA 16
HP: 43
AC: 17 (Chain Mail + Defense fighting style)
Proficiencies: Land Vehicles, artisan's tools, Perception, Acrobatics, Animal Handling, Survival
Cantrips: Booming Blade, Lightning Lure
Spells: Hellish Rebuke, Hex
Spell Slots: 1


11th level:
Fighter 2/Hexblade 1/Samurai Fighter 4/Ranger 1/Monk 1/Wizard 1/Bard 1
Stats: STR 13, DEX 14, CON 14, INT 13, WIS 13, CHA 18
HP: 89
AC: 18 (Half-plate + Defense fighting style)
Proficiencies: Land Vehicles, artisan's tools, Perception, Acrobatics, Animal Handling, Survival, Insight, Persuasion, musical instrument
Cantrips: Booming Blade, Lightning Lure, Light, Prestidigitation, Mage Hand, Minor Illusion, Thunderclap
Spells: Hellish Rebuke, Hex, Feather Fall, Expeditious Retreat, Find Familiar(R), Identify(R), Comprehend Languages(R), Unseen Servant(R), Bane, Charm Person, Distort Value, Dissonant Whispers
Spell Slots: 4

17th level:
Fighter 2/Hexblade 1/Samurai Fighter 4/Ranger 1/Monk 1/Wizard 1/Bard 1/Wild Magic Sorcerer 1/Barbarian 1/Life Cleric 1/Druid 1/Artificer 2
Stats: STR 13, DEX 14, CON 14, INT 13, WIS 13, CHA 18
HP: 132
AC: 19 (Half-plate + Defense fighting style + Enhanced Defense infusion)
Proficiencies: Land Vehicles, artisan's tools, Perception, Acrobatics, Animal Handling, Survival, Insight, Persuasion, musical instrument, Thieves' Tools, Tinker's Tools
Cantrips: Booming Blade, Lightning Lure, Light, Prestidigitation, Mage Hand, Minor Illusion, Thunderclap, Chill Touch, Firebolt, Frostbite, Ray of Frost, Guidance, Mending, Thaumaturgy, Mold Earth, Shape Water, Druidcraft, Dancing Lights, Spare the Dying
Spells: Hellish Rebuke, Hex, Feather Fall, Expeditious Retreat, Find Familiar(R), Identify(R), Comprehend Languages(R), Unseen Servant(R), Bane, Charm Person, Distort Value, Dissonant Whispers, Absorb Elements, Shield, Cure Wounds, Bless, Healing Word, Detect Magic(R), Goodberry, something from the druid spell list, Alarm (R)
Spell Slots: 11

20th level:
Fighter 2/Hexblade 1/Samurai Fighter 4/Ranger 1/Monk 1/Wizard 1/Bard 1/Wild Magic Sorcerer 1/Barbarian 1/Life Cleric 1/Druid 1/Artificer 2/Rogue 1/Paladin 2
Stats: STR 13, DEX 14, CON 14, INT 13, WIS 13, CHA 18
HP: 155
AC: 19 (Half-plate + Defense fighting style + Enhanced Defense infusion)
Proficiencies: Land Vehicles, artisan's tools, Perception, Acrobatics, Animal Handling, Survival, Insight, Persuasion(E), musical instrument, Thieves' Tools, Tinker's Tools, Deception
Cantrips: Booming Blade, Lightning Lure, Light, Prestidigitation, Mage Hand, Minor Illusion, Thunderclap, Chill Touch, Firebolt, Frostbite, Ray of Frost, Guidance, Mending, Thaumaturgy, Mold Earth, Shape Water, Druidcraft, Dancing Lights, Spare the Dying
Spells: Hellish Rebuke, Hex, Feather Fall, Expeditious Retreat, Find Familiar(R), Identify(R), Comprehend Languages(R), Unseen Servant(R), Bane, Charm Person, Distort Value, Dissonant Whispers, Absorb Elements, Shield, Cure Wounds, Bless, Healing Word, Detect Magic(R), Goodberry, something from the druid spell list, Alarm (R), Divine Favor, Lesser Restoration, Dispel Magic, Banishment, Staggering Smite
Spell Slots: 12