dead ringer vs look-alike

dead ringer and look-alike both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead ringer	Yes	No	No	No
look-alike	Yes	Yes	No	No

As nouns, look-alike is a hypernym of dead ringer; that is, look-alike is a word with a broader meaning than dead ringer:

dead ringer: a person who is almost identical to another
look-alike: someone who closely resembles a famous person (especially an actor)

Other hypernyms of dead ringer include double, image.

dead ringer (noun)	look-alike (noun)
a person who is almost identical to another	someone who closely resembles a famous person (especially an actor)

dead ringer (adjective)	look-alike (adjective)
	resembling closely