From the introduction:
Pugilist: Arrows rain down around her as she runs towards the hobgoblins. Desperate to close the distance, the half-orc fights through the sting of a dozen cuts to reach her foes. The pain only makes her stronger. As she descends on the hobgoblins she swings wildly, knocking hobgoblins to their feet and sending the rest scattering before her.
He braces himself for the impact as the orc rushes him. Then the orc makes a mistake, telegraphing its next move, and that’s all the opening the human needs. He ducks beneath the orc’s wide swing then raises both hands high above his head and brings them down on the orc’s back, throwing the brute to the ground.
The dwarf smiles broadly and chuckles as the petty noble raises his hand to strike him for the impudent remark. Quick as a flash the dwarf shatters the bottle in his hand against the bar and puts it between himself and the noble. The noble flinches, stumbles backward, and runs away as the dwarf turns back to the bar to order another round.
Wherever they come from, pugilists live a rough and tumble life that leaves them full of determination and reckless from overconfidence or desperation. In a fight they can channel this strength of character to dig deep and fight off foes in greater strength of numbers, arms, and armor than anyone else would think possible.
See also Additional Fight Clubs for Pugilist (5e).