WordNet (r) 3.0 (2006):

tough guy
    n 1: someone who bullies weaker people [syn: tough guy, plug-
         ugly]

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "tough guy":
   Antaeus, Atlas, Briareus, Brobdingnagian, Charles Atlas, Cyclops,
   Goliath, Hercules, Mafioso, Polyphemus, Samson, Superman, Tarzan,
   Titan, Young Turk, beast, beldam, berserk, berserker, bomber,
   brute, bully, bullyboy, colossus, demon, devil, dragon, fiend,
   fire-eater, firebrand, fury, giant, goon, gorilla, gunsel,
   hardnose, hell-raiser, hellcat, hellhound, hellion, holy terror,
   hood, hoodlum, hothead, hotspur, incendiary, killer, mad dog,
   madcap, monster, mugger, muscle man, powerhouse, rapist,
   revolutionary, savage, she-wolf, spitfire, stalwart, strong man,
   strong-arm man, termagant, terror, terrorist, the mighty,
   the strong, tiger, tigress, tough, tower of strength,
   ugly customer, violent, virago, vixen, wild beast, witch, wolf