flatter vs butter up

flatter and butter up both are verbs.

Word	Noun	Adjective	Verb	Adverb
flatter	No	No	Yes	No
butter up	No	No	Yes	No

As verbs, butter up is a hyponym of flatter; that is, butter up is a word with a more specific, narrower meaning than flatter:

Other hyponyms of flatter include soft-soap, adulate, stroke, bootlick, fawn, kotow, kowtow, suck up, toady, truckle, brown-nose.

flatter (verb)	butter up (verb)
praise somewhat dishonestly	flatter with the intention of getting something