Pit Fighter

From down in the pits, these warriors have been dragged through lots, be it as a punishment or through their own choice. The pit fighter is one who has toughed it out through the daily blood sport in the pits, gaining money and fame through fighting. They have learnt lots from their time in the pits and have been able to survive better than the rest. 

Improved Unarmed Strike

Starting at level 3, the unarmed strike of the character is improved to 1d8 + str + proficiency bludgeoning. Additionally an unarmed strike can be used as a bonus action to deal 1d6 + str bludgeoning. 

Pit Grit

Beginning at level 6, the pit fighter can use an action to gain temporary hit points equal to the damage taken in the previous turn + double their con modifier. This can be used twice before needing a long rest. 

They also gain proficiency in survival. 

Underdog Strength

Starting from level 10, when fighting against 3+ opponents of a cr above or equal to the player's level, the unarmed strike damage goes from 1d8 to 1d10 on an action. 

Flashy Moves

At level 14, when landing a critical hit with an unarmed strike, instead of rolling 2 dice, 3 dice gets rolled.