killjoy vs persona non grata

killjoy and persona non grata both are nouns.

Word	Noun	Adjective	Verb	Adverb
killjoy	Yes	No	No	No
persona non grata	Yes	No	No	No

As nouns, persona non grata is a hypernym of killjoy; that is, persona non grata is a word with a broader meaning than killjoy:

Other hypernyms of killjoy include unwelcome person.

killjoy (noun)	persona non grata (noun)
someone who spoils the pleasure of others	a person who for some reason is not wanted or welcome
	a diplomat who is unacceptable to the government to which he is sent