ladies' man vs lady killer

ladies' man and lady killer both are nouns.

Word	Noun	Adjective	Verb	Adverb
ladies' man	Yes	No	No	No
lady killer	Yes	No	No	No

As nouns, ladies' man and lady killer are synonyms defined as:

Other synonyms of ladies' man include seducer.

ladies' man (noun)	lady killer (noun)
a man who takes advantage of women	a man who takes advantage of women