keen vs bang-up

keen is a noun but bang-up is not a noun.

Word	Noun	Adjective	Verb	Adverb
keen	Yes	Yes	Yes	No
bang-up	No	Yes	No	No

As adjectives, keen and bang-up are synonyms defined as:

Other synonyms of keen include bully, corking, cracking, dandy, great, groovy, neat, nifty, not bad, old, peachy, slap-up, smashing, swell.

keen (noun)	bang-up (noun)
a funeral lament sung with loud wailing

keen (adjective)	bang-up (adjective)
excellent	excellent
intense or sharp
having or demonstrating ability to recognize or draw fine distinctions
having a sharp cutting edge or point
painful as if caused by a sharp instrument

keen (verb)	bang-up (verb)
express grief verbally