killer vs strangler

killer and strangler both are nouns.

Word	Noun	Adjective	Verb	Adverb
killer	Yes	No	No	No
strangler	Yes	No	No	No

As nouns, strangler is a hyponym of killer; that is, strangler is a word with a more specific, narrower meaning than killer:

killer (noun)	strangler (noun)
predatory black-and-white toothed whale with large dorsal fin; common in cold seas	someone who kills by strangling
a difficulty that is hard to deal with	an epiphytic vine or tree whose aerial roots extend down the trunk of a supporting tree and coalesce around it eventually strangling the tree
someone who causes the death of a person or animal
the causal agent resulting in death