agonist vs fictitious character

agonist and fictitious character both are nouns.

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

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

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

Other hypernyms of agonist include character, fictional character.

agonist (noun)	fictitious 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