enemy vs opponent

enemy and opponent both are nouns.

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

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

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

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

enemy (noun)	opponent (noun)
an opposing military force	someone who offers opposition
any hostile group of people	a contestant that you are matched against
an armed adversary (especially a member of an opposing military force)
a personal enemy

enemy (adjective)	opponent (adjective)
	characterized by active hostility