underdog
n. countablen. a person or team that is expected to lose a competition or struggle. People often support them because it is exciting to see them win against the odds.
n. a competitor thought to have little chance of winning a fight or contest. Often used to describe a person or group in a position of disadvantage within a social or political struggle.
The local team was the underdog in the final match.
Despite being the underdog in the election, the young candidate won by a surprising margin.
The film follows the classic narrative of a determined underdog who overcomes systemic obstacles to achieve victory against a much more powerful opponent.
From under- + dog.
Commonly used with the definite article ('the underdog') when referring to the general concept of the disadvantaged party.