duelist vs antagonist

duelist and antagonist both are nouns.

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

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

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

duelist (noun)	antagonist (noun)
a person who fights duels	a drug that neutralizes or counteracts the effects of another drug
	a muscle that relaxes while another contracts
	someone who offers opposition