rescuer vs doer

rescuer and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
rescuer	Yes	No	No	No
doer	Yes	No	No	No

As nouns, doer is a hypernym of rescuer; that is, doer is a word with a broader meaning than rescuer:

Other hypernyms of rescuer include actor, worker.

rescuer (noun)	doer (noun)
someone who saves something from danger or violence	a person who acts and gets things done
a person who rescues you from harm or danger