loose cannon vs doer

loose cannon and doer both are nouns.

Word	Noun	Adjective	Verb	Adverb
loose cannon	Yes	No	No	No
doer	Yes	No	No	No

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

loose cannon: a person who is expected to perform a particular task but who is out of control and dangerous
doer: a person who acts and gets things done

Other hypernyms of loose cannon include actor, worker.

loose cannon (noun)	doer (noun)
a person who is expected to perform a particular task but who is out of control and dangerous	a person who acts and gets things done