agonist vs protagonist

agonist and protagonist both are nouns.

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

As nouns, agonist and protagonist are synonyms defined as:

agonist (noun)	protagonist (noun)
(biochemistry) a drug that can combine with a receptor on a cell to produce a physiological reaction	a person who backs a politician or a team etc.
a muscle that contracts while another relaxes	the principal character in a work of fiction
someone involved in a contest or battle (as in an agon)
the principal character in a work of fiction