flatterer vs ass-kisser

flatterer and ass-kisser both are nouns.

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

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

flatterer: a person who uses flattery
ass-kisser: a person who tries to please someone in order to gain a personal advantage

Other hyponyms of flatterer include crawler, lackey, sycophant, toady.

flatterer (noun)	ass-kisser (noun)
a person who uses flattery	a person who tries to please someone in order to gain a personal advantage