cracksman vs stealer

cracksman and stealer both are nouns.

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

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

cracksman: a thief who breaks open safes to steal valuable contents
stealer: a criminal who takes property belonging to someone else with the intention of keeping it or selling it

Other hypernyms of cracksman include thief.

cracksman (noun)	stealer (noun)
a thief who breaks open safes to steal valuable contents	a criminal who takes property belonging to someone else with the intention of keeping it or selling it