arsonist vs malefactor

arsonist and malefactor both are nouns.

Word	Noun	Adjective	Verb	Adverb
arsonist	Yes	No	No	No
malefactor	Yes	No	No	No

As nouns, malefactor is a hypernym of arsonist; that is, malefactor is a word with a broader meaning than arsonist:

arsonist: a criminal who illegally sets fire to property
malefactor: someone who has committed a crime or has been legally convicted of a crime

Other hypernyms of arsonist include criminal, crook, felon, outlaw.

arsonist (noun)	malefactor (noun)
a criminal who illegally sets fire to property	someone who has committed a crime or has been legally convicted of a crime