hit man vs manslayer

hit man and manslayer both are nouns.

Word	Noun	Adjective	Verb	Adverb
hit man	Yes	No	No	No
manslayer	Yes	No	No	No

As nouns, manslayer is a hypernym of hit man; that is, manslayer is a word with a broader meaning than hit man:

hit man: a professional killer who uses a gun
manslayer: a criminal who commits homicide (who performs the unlawful premeditated killing of another human being)

Other hypernyms of hit man include liquidator, murderer.

hit man (noun)	manslayer (noun)
a professional killer who uses a gun	a criminal who commits homicide (who performs the unlawful premeditated killing of another human being)