antihero vs agonist

antihero and agonist both are nouns.

Word	Noun	Adjective	Verb	Adverb
antihero	Yes	No	No	No
agonist	Yes	No	No	No

As nouns, agonist is a hypernym of antihero; that is, agonist is a word with a broader meaning than antihero:

antihero: a protagonist who lacks the characteristics that would make him a hero (or her a heroine)
agonist: the principal character in a work of fiction

Other hypernyms of antihero include protagonist.

antihero (noun)	agonist (noun)
a protagonist who lacks the characteristics that would make him a hero (or her a heroine)	(biochemistry) a drug that can combine with a receptor on a cell to produce a physiological reaction
	a muscle that contracts while another relaxes
	someone involved in a contest or battle (as in an agon)
	the principal character in a work of fiction