unnatural
1 aberrant, abnormal, anomalous, irregular, odd, perverse, perverted, unusual
2 bizarre, extraordinary, freakish, outlandish, queer, strange, supernatural, unaccountable, uncanny
3 affected, artificial, assumed, contrived, factitious, false, feigned, forced, insincere, laboured, mannered, phoney or phony (informal) self-conscious, stagy, stiff, stilted, strained, studied, theatrical
4 brutal, callous, cold-blooded, evil, fiendish, heartless, inhuman, monstrous, ruthless, savage, unfeeling, wicked
Antonyms
1 & 2 normal, ordinary, typical
3 genuine, honest, natural, sincere, unaffected, unfeigned, unpretentious
4 caring, humane, loving, warm