Underachiever (noun)

1. A person who performs or achieves less than expected or desired.
2. A person who fails to reach their potential.

Origin:

Mid 20th century: blend of under- and achiever.

Examples:

1. He was labeled an underachiever by his teachers.
2. The team had several underachievers on its roster.
3. He was considered an underachiever in his field.
4. The company's underachievers were let go in the recent layoffs.
5. The student was considered an underachiever by her classmates.