Pugilist

Wherever they come from, pugilists live a rough and tumble life that leaves them full of determination, either from overconfidence or desperation. In a fight they can channel this strength of character to dig deep and fight off foes with greater strength of numbers, arms, or armor, using an unorthodox fighting style that lacks the formal teachings of monks yet bears a certain resemblance to it. They rely on fast, decisive strikes and sure-footed evasion to dispatch foes efficiently and brutally, using their fists to strike with as much if not more brutality and power than that of normal weapons.

Fisticuffs

When you choose this archetype at 3rd level, your physicality becomes rarely matched, to the point of fighting with nothing but your fists. You gain proficiency in the Athletics if you aren't proficient already.

Additionally, when you use the Attack action with an unarmed strike, you can make one unarmed strike as a bonus action, and your unarmed strikes ignore resistance and immunity to nonmagical attacks. Finally, when you are wielding light armor, you may use your Strength modifier for it, instead of Dexterity (override in character sheet).

Old One-Two

Also at 3rd level, you become adept at chaining strikes, one after the other. When you hit a creature with two unarmed strikes on the same turn, you can choose one of the following effects:

• The next attack you make against the target has a bonus to hit equal to your proficiency bonus (this is an addition to its normal bonus to hit).
• The target is deafened until the start of your next turn.
• The target is pushed 5 feet back if they are at most one size larger than you.
• The next attack you make against the creature deals extra damage to your proficiency bonus.

Bob and Weave

By 7th level, your experience getting into scraps and brawls has taught you how to deftly avoid enemy attacks and then exploit their openness with brutal counterattacks. After a creature misses you with an attack, you can use your reaction and make a number of unarmed strikes against them equal to the number of attacks you can make with your Attack action.

Not Out Yet

When you reach 10th level, you've become well accustomed to shaking off physical punishment and knockout blows. At the end of your turn, if you are stunned or unconscious, you can use your reaction to end the condition, gain 1 hit point, and gain temporary hit points equal to your fighter level.

You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.

Bloodied But Unbowed

When you reach 15th level, whenever you take damage that reduces you to half your maximum hit points or less, you can use your reaction to gain temporary hit points equal to twice your fighter llevel + twice your Constitution modifier. You can use this featue twice, and gain all expended uses when you finish a short or long rest.

Iron Chin

At 18th level, you attain the pinnacle of resilience in battle. Whenever you roll initiative, you gain temporary hit points equal to half your hit point maximum. These temporary hit points vanish at the end of combat.