champion vs expert

champion and expert both are nouns.

Word	Noun	Adjective	Verb	Adverb
champion	Yes	Yes	Yes	No
expert	Yes	Yes	No	No

As nouns, expert is a hypernym of champion; that is, expert is a word with a broader meaning than champion:

champion (noun)	expert (noun)
someone who fights for a cause	a person with special knowledge or ability who performs skillfully
someone who has won first place in a competition
a person who backs a politician or a team etc.
someone who is dazzlingly skilled in any field

champion (adjective)	expert (adjective)
holding first place in a contest	having or showing knowledge and skill and aptitude
	of or relating to or requiring special knowledge to be understood

champion (verb)	expert (verb)
protect or fight for as a champion