ass-kisser vs groveller

ass-kisser and groveller both are nouns.

Word	Noun	Adjective	Verb	Adverb
ass-kisser	Yes	No	No	No
groveller	Yes	No	No	No

As nouns, groveller is a hyponym of ass-kisser; that is, groveller is a word with a more specific, narrower meaning than ass-kisser:

ass-kisser: a person who tries to please someone in order to gain a personal advantage
groveller: someone who humbles himself as a sign of respect; who behaves as if he had no self-respect

Other hyponyms of ass-kisser include apple polisher, bootlicker, fawner, groveler, truckler, goody-goody.

ass-kisser (noun)	groveller (noun)
a person who tries to please someone in order to gain a personal advantage	someone who humbles himself as a sign of respect; who behaves as if he had no self-respect