Mr Hyde, from the original novel. Hint: contrary to popular movie portrayals, Mr Hyde is *not* a giant mutant titan. Imagine, instead, a man whose entire body is tensed and contorted, the muscles wound up impossibly tight. He looks dwarfed or hunched, but becomes an unstoppable juggernaut when enraged. The personality and behaviour are even more unsettling than the appearance.

Then there's the pig character from the ancient Chinese epic, Journey to the West. He's a man who was supposed to be reincarnated into a new human body, but there was a clerical error at the reincarnation wheel. Instead of being born from a human mother, he was impregnated into a pig. He emerged as a demi-human pig-monster, shunned and feared and eventually becoming a cannibalistic terror until recruited by the monk Tripitaka on his titular journey, becoming a valued - if dubious - companion.
Sure he winds up as a hero, but his concepts and origins are rather bat. Especially since the character was first written in the sixteenth century.