WordNet sense 1 (a cruel wicked and inhuman person):

demon, devil, fiend, ogre

WordNet sense 2 (someone or something that is abnormally large and powerful):

behemoth, colossus, giant, goliath

WordNet sense 3 (a person or animal that is markedly unusual or deformed):

freak, monstrosity, lusus naturae

WordNet sense 4 ((medicine) a grossly malformed and usually nonviable fetus):

teras