ruler vs doer

ruler and doer both are nouns.

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

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

Other hypernyms of ruler include actor, worker.

ruler (noun)	doer (noun)
measuring stick consisting of a strip of wood or metal or plastic with a straight edge that is used for drawing straight lines and measuring lengths	a person who acts and gets things done
a person who rules or commands