stoolpigeon vs betrayer

stoolpigeon and betrayer both are nouns.

Word	Noun	Adjective	Verb	Adverb
stoolpigeon	Yes	No	No	No
betrayer	Yes	No	No	No

As nouns, betrayer is a hypernym of stoolpigeon; that is, betrayer is a word with a broader meaning than stoolpigeon:

stoolpigeon: someone acting as an informer or decoy for the police
betrayer: one who reveals confidential information to the police or other authority

Other hypernyms of stoolpigeon include blabber, informer, rat, squealer.

stoolpigeon (noun)	betrayer (noun)
someone acting as an informer or decoy for the police	a person who says one thing and does another
	one who reveals confidential information to the police or other authority