militant vs activist

militant and activist both are nouns.

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

As nouns, militant and activist are synonyms defined as:

militant (noun)	activist (noun)
a militant reformer	a militant reformer

militant (adjective)	activist (adjective)
showing a fighting disposition	advocating or engaged in activism
disposed to warfare or hard-line policies
engaged in war