Even inside the same combat system (boxing, karate, etc), there’s many different styles of fighting . I’ve tried to translate that for my D&D 5e Streets & Turmoil setting.
As it is far easier and less risky to take what already exists rather than homebrew everything from scratch, I’ve started with looking at the options already available. When I couldn’t find any, I’ve resorted to basic homebrewing, tinkering with the fighter class feature fighting styles and champion subclass battle maneuvers.
The slugger isn’t about subtlety, his output his low, but when he do strikes, all of his body is committed to it.
New champion battle maneuver: Power Punch
When you make an unarmed melee attack on your turn, you can choose to have disadvantage. When you do so, add twice the superiority die to the attack’s damage roll.
Clinch holds, elbows, headbutts, eye gouge, bites and hidden weapons: anything goes in dirty boxing, less a style than a willingness to uses every possible means to achieve victory.
Okay, I just saw that the Tavern Brawler feat is exactly that… I’ll just rename it.
The strength of an unorthodox style resides in the fact that it’s something so rarely displayed that almost any opponent feels awkward against its practitioner.
New fighter’s fighting style:
When a creature makes a melee attack against you , it must make a wisdom saving throw. On a failed save, the creature provokes an attack of opportunity, if you hit, add the superiority die to the attack’s damage roll.