enemy vs antagonist

enemy and antagonist both are nouns.

Word	Noun	Adjective	Verb	Adverb
enemy	Yes	No	No	No
antagonist	Yes	No	No	No

As nouns, antagonist is a hypernym of enemy; that is, antagonist is a word with a broader meaning than enemy:

enemy: an armed adversary (especially a member of an opposing military force)
antagonist: someone who offers opposition

Other hypernyms of enemy include adversary, opponent, opposer, resister.

enemy (noun)	antagonist (noun)
an opposing military force	a drug that neutralizes or counteracts the effects of another drug
any hostile group of people	a muscle that relaxes while another contracts
an armed adversary (especially a member of an opposing military force)	someone who offers opposition
a personal enemy