looter vs stealer

looter and stealer both are nouns.

Word	Noun	Adjective	Verb	Adverb
looter	Yes	No	No	No
stealer	Yes	No	No	No

As nouns, stealer is a hypernym of looter; that is, stealer is a word with a broader meaning than looter:

looter: someone who takes spoils or plunder (as in war)
stealer: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of looter include thief.

looter (noun)	stealer (noun)
someone who takes spoils or plunder (as in war)	a criminal who takes property belonging to someone else with the intention of keeping it or selling it