highjacker vs malefactor

highjacker and malefactor both are nouns.

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

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

highjacker: someone who uses force to take over a vehicle (especially an airplane) in order to reach an alternative destination
malefactor: someone who has committed a crime or has been legally convicted of a crime

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

highjacker (noun)	malefactor (noun)
a holdup man who stops a vehicle and steals from it	someone who has committed a crime or has been legally convicted of a crime
someone who uses force to take over a vehicle (especially an airplane) in order to reach an alternative destination