friend vs protagonist

friend and protagonist both are nouns.

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

As nouns, friend and protagonist are synonyms defined as:

Other synonyms of friend include admirer, booster, champion, supporter.

friend (noun)	protagonist (noun)
a person you know well and regard with affection and trust	a person who backs a politician or a team etc.
a person with whom you are acquainted	the principal character in a work of fiction
an associate who provides cooperation or assistance
a person who backs a politician or a team etc.