booster vs proponent

booster and proponent both are nouns.

Word	Noun	Adjective	Verb	Adverb
booster	Yes	No	No	No
proponent	Yes	No	No	No

As nouns, proponent is a hypernym of booster; that is, proponent is a word with a broader meaning than booster:

Other hypernyms of booster include advocate, advocator, exponent.

booster (noun)	proponent (noun)
an additional dose that makes sure the first dose was effective	a person who pleads for a cause or propounds an idea
the first stage of a multistage rocket
an amplifier for restoring the strength of a transmitted signal
a thief who steals goods that are in a store
someone who is an active supporter and advocate
a person who backs a politician or a team etc.