Noun
underachiever (plural underachievers)
One who underachieves, i.e. performs less well than expected. [from 1950s]
Antonym: overachiever
If it turns out that there is a God... the worst that you can say about him is that basically he's an underachiever. Woody Allen
In school, I was an underachiever. Henry Winkler
The important thing, I think, is not to be bitter. You know, if it turns out that there is a God, I don't think that he's evil. I think that the worst you can say about him is that basically he's an underachiever. Woody Allen