beast, monster, asshole

(やじゅう) A sexual predator, someone who is not just a rapist but also physically wild or animalistic in their lust.
(ちくしょう) Comes from a word for beast, but it’s used just like asshole! You asshole! Fuck!
(けもの) Used about literal animals – not necessarily the hugest or scariest, but animals that are both violent AND unclean, like the hyena. Also used about people who behave like those animals.
(もうじゅう) A big scary animal – lion, bear. Not used about people even metaphorically.