Winner
an opponent is a rival
Enemy , antagonist are several synonyms . Also; opponent, rival, competitor, foe, contestant
Opponent
adversary, rival, foe, opponent
The ultimate opponent, the great enemy.
rival, adversary, opponent, enemy, contender
opponent, attacker, invader, rival
colleague, associate, teammate proponent, supporter, backer (of an idea)
Adversary, rival, enemy, challenger
Antagonist simply means, Rival or Opponent.
enemy, opposer, rival, opponent
Foe Rival Nemesis Villain Opponent