activist vs reformist

activist and reformist both are nouns.

Word	Noun	Adjective	Verb	Adverb
activist	Yes	Yes	No	No
reformist	Yes	Yes	No	No

As nouns, reformist is a hypernym of activist; that is, reformist is a word with a broader meaning than activist:

Other hypernyms of activist include crusader, meliorist, reformer, social reformer.

activist (noun)	reformist (noun)
a militant reformer	a disputant who advocates reform

activist (adjective)	reformist (adjective)
advocating or engaged in activism	favoring or promoting reform (often by government action)