thief vs malefactor

thief and malefactor both are nouns.

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

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

thief: a criminal who takes property belonging to someone else with the intention of keeping it or selling it
malefactor: someone who has committed a crime or has been legally convicted of a crime

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

thief (noun)	malefactor (noun)
a criminal who takes property belonging to someone else with the intention of keeping it or selling it	someone who has committed a crime or has been legally convicted of a crime