rapist vs assailant

rapist and assailant both are nouns.

Word	Noun	Adjective	Verb	Adverb
rapist	Yes	No	No	No
assailant	Yes	No	No	No

As nouns, assailant is a hypernym of rapist; that is, assailant is a word with a broader meaning than rapist:

Other hypernyms of rapist include aggressor, assaulter, attacker, criminal, crook, felon, malefactor, outlaw.

rapist (noun)	assailant (noun)
someone who forces another to have sexual intercourse	someone who attacks