nonachiever vs underachiever

nonachiever and underachiever both are nouns.

Word	Noun	Adjective	Verb	Adverb
nonachiever	Yes	No	No	No
underachiever	Yes	No	No	No

As nouns, nonachiever and underachiever are synonyms defined as:

nonachiever and underachiever: a student who does not perform as well as expected or as well as the IQ indicates

Other synonyms of nonachiever include underperformer.

nonachiever (noun)	underachiever (noun)
a student who does not perform as well as expected or as well as the IQ indicates	a student who does not perform as well as expected or as well as the IQ indicates