opponent vs enemy

opponent and enemy both are nouns.

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

As nouns, enemy is a hyponym of opponent; that is, enemy is a word with a more specific, narrower meaning than opponent:

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

Other hyponyms of opponent include dueler, duelist, dueller, duellist, foe, foeman, opposition, Luddite, withstander.

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

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