competitor, rival, challenger, contestant, adversary, opponent, aspirant, candidate, entrant, participant
warrior - combatant - soldier - brawler - pugilist - contender - battler - scrapper - gladiator - champion - duelist - assailant - aggressor - trooper - mercenary - militant - belligerent - bruiser - grappler - ruffian - enforcer - paladin - knight - samurai - ninja - commando - marine - ranger - infantryman - guerrilla - partisan - swashbuckler - avenger - protector - defender - guardian - hero - stalwart - prizefighter