hitman vs liquidator

hitman and liquidator both are nouns.

Word	Noun	Adjective	Verb	Adverb
hitman	Yes	No	No	No
liquidator	Yes	No	No	No

As nouns, liquidator is a hypernym of hitman; that is, liquidator is a word with a broader meaning than hitman:

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

Other hypernyms of hitman include manslayer, murderer.

hitman (noun)	liquidator (noun)
a professional killer who uses a gun	(law) a person (usually appointed by a court of law) who liquidates assets or preserves them for the benefit of affected parties
	a criminal who commits homicide (who performs the unlawful premeditated killing of another human being)