agonist vs fictional character

agonist and fictional character both are nouns.

Word	Noun	Adjective	Verb	Adverb
agonist	Yes	No	No	No
fictional character	Yes	No	No	No

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

agonist: the principal character in a work of fiction
fictional character: an imaginary person represented in a work of fiction (play or film or story)

Other hypernyms of agonist include character, fictitious character.

agonist (noun)	fictional character (noun)
(biochemistry) a drug that can combine with a receptor on a cell to produce a physiological reaction	an imaginary person represented in a work of fiction (play or film or story)
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