Implacable

The Implacable is a Variant Class for the Barbarian that appeared in Dungeons & Dragons 3.5E

Third Edition

Whereas most barbarians prefer to wear as little armor as they could get away with, maybe going as heavy as hide armor, an Implacable is all about tanking and thus holds no reservations about wearing full suits of plate armor while charging in face-first to bust heads.

As a variant class, the Implacable doesn't replace much, but what it does change is quite significant.

• Gain proficiencies in all armor and shields except tower shields. Oh yeah, time to get mad in chainmail.
• Lose Fast Movement. A bit of a shame since heavy armor tends to jeapordize speed, but them's the breaks.
• Rather than the typical benefits of Rage, an Implacable gains "Resilient Rage", gaining bonuses to Dexterity, Constitution and Will saves as well as Damage Reduction. This scales at the same time as regular Rage.
  • On one hand, the Dex bonus won't mean shit for if you're jumping towards heavy armor, since the max Dexterity for those is practically nonexistent - what you do get out of it is a minor boost to offset the armor check penalties provided by said armor as well as the boosts to Initiative and Reflex saves. However, keeping with Medium Armor gives you all of those benefits on top of the AC boost. Keep in mind either way that you'll still need to keep your Strength high more than ever since you'll lack any attack boosts from melee...unless you just want to be a dodge-tank. Weapon Finesse help too.

5E

5E introduced the Path of the Battlerager subclass as part of the "Sword Coast Adventurer's Guide". While the heavily armored bit is here, the damage-tanking bit isn't quite so due to Rage already giving resistance to mundane damage as a default. The big issue is that it traps you in a single suit of armor that's not the most impressive due to it only being AC14 with a Dex cap of +2, with no way to improve that without magical armor and no value outside of it. The other strike against it (if you could call it that) is the race restriction to dwarves only - though that's more due to the book being set in the Forgotten Realms.

• Level 3 - Battlerager Armor: You gain proficiency in spiky armor that's about as good as scale mail but also can be used to punch things as a bonus action for 1d4+Str damage. Grappling also deals 3 damage if you pull it off.
  • This all really considered not that great due to the damage really not amounting to much, though the punch being a bonus action won't be an issue for you. The grapple though is atrocious.
• Level 6 - Reckless Abandon: When you use Reckless Attack while raging, you gain temporary HP equal to Con mod for the rest of the rage.
  • Expect to use this a lot. Between your locked AC and Reckless Attack giving enemies advantage to hit you, this will be used quite a bit.
• Level 10 - Battlerager Charge: You can dash as a bonus action while raging.
  • Neat, since this can throw you in the way of an enemy very quickly. Will sacrifice the extra punch though.
• Level 14 - Spiked Retribution: Any enemies that hit you with a melee attack while wearing the spiked armor and while you are still conscious take 3 damage.
  • Decent, since any enemies that have multi-attack will have that damage stack up. That said, this is still trapping you in the armor.

Pathfinder

Pathfinder did keep the idea of a heavily-armored barbarian around, but not in any recognizable way.

The Armored Hulk Archetype from "Ultimate Combat" kept the heavily-armored part, but less of the dodge-tanking potential. Notably, Rage is identical here, so you'll need any means to offset any damage taken beyond the class' native Damage Reduction.

• Gain proficiency in heavy armor.
• Replaces Fast Movement with Indomitable Stance. Gain +1 to combat maneuvers and to CMD on overrun checks and Reflex saves against trampling. Gain +1 to AC against charge attacks and +1 to hit and damage on the charge.
• Replaces Uncanny Dodge with Armored Swiftness. Gain a +5 foot speed bonus when wearing medium or heavy armor, but not beyond their native speed. Decent enough tradeoff for the typical speed boost.
• Replaces Trap Sense with Resilience of Steel. Gain a +1 bonus to AC against all crit confirms. Improves by +1 every 3 levels.
• Replaces Improved Uncanny Dodge with Improved Armored Swiftness. That speed boost is now upped to +10 feet and is applicable to any armor, but shuts off if you're carrying a heavy load.
• While not a feature, there are some recommended Rage Powers to consider: Boasting Taunt (Special demoralize action when charging with a bonus for drinking), Guarded Life (regular and greater; if dropped to 0 HP, some of the excess damage is converted to nonlethal damage and auto-stabilize), Guarded Stance (Grants a temporary bonus to AC against melee attacks for a number of rounds equal to Con mod), Increased Damage Reduction (Improves the class' damage reduction while raging), No Escape (1/rage ability to chase enemies who withdraw), Overbearing Advance (Overrun maneuvers now deal Str mod damage when raging), Rolling Dodge (Guarded Stance but against ranged attacks), Reflexive Dodge (Rolling Dodge's bonus now apples to Reflex saves), Unexpected Strike (1/rage attack against anyone who moves within reach as an AoO)

For the "tank anything and everything" utility, the "APG" provides the Invulnerable Rager, which can't stack with the Armored Hulk above. It does, however, open up to archetype stacking a bit more easily due to replacing less abilities.

• Replaces Uncanny Dodge, Improved Uncanny Dodge and Damage Reduction for Damage Reduction equal to half the class level, which is very hard to come across, especially at lower levels.
• Replaces Trap Sense with Extreme Endurance, granting resistance to either extreme hot or cold as if under the Endure Elements spell. This also includes +1 to either fire or cold resistance for every 3 levels after.
• While not a feature, there are some recommended Rage Powers to consider: Come and Get Me (Gives enemies a bonus to hit them, but risks an AoO in return), Guarded Life (regular and greater; if dropped to 0 HP, some of the excess damage is converted to nonlethal damage and auto-stabilize), Guarded Stance (Grants a temporary bonus to AC against melee attacks for a number of rounds equal to Con mod), Increased Damage Reduction (Improves the class' damage reduction while raging), No Escape (1/rage ability to chase enemies who withdraw), Reckless Abandon (Increase Rage's AC penalty for a bonus to hit), Rolling Dodge (Guarded Stance but against ranged attacks), Inspire Ferocity (Reckless Abandon can be shared with allies for Cha mod - 1 rounds), Renewed Vigor (1/day ability to heal HP while raging)