antagonist
US /ænˈtæɡ.ən.ɪst/
UK /ænˈtæɡ.ən.ɪst/

1.
antagonista, adversário, oponente
a person who actively opposes or is hostile to someone or something; an adversary.
:
•
The hero faced his main antagonist in the final battle.
O herói enfrentou seu principal antagonista na batalha final.
•
She was a fierce antagonist of the new policy.
Ela era uma feroz antagonista da nova política.