lunge/dash attack is best, just be at 3 meters distance to your opponent, lunge with a quick (and really heavy!) punch, then immediately move away to same distance, repeat
it usually takes 2-3 such punches and one minute of time to win
i'm doing pugilism matches only to heal, so i always almost at zero health and always choose most skilled opponent for more money, and yet i don't remember when last time i lose pugilism match with that tactic