Synonyms for "antagonist":

 Here are some synonyms for "antagonist":

General Opponents:

• Opponent
• Adversary
• Rival
• Competitor
• Contender
• Opposer

More Hostile Opponents:

• Enemy
• Foe
• Hostile
• Attacker
• Assailant
• Combatant

Specific Types of Antagonists:

• Nemesis
• Archenemy
• Archfoe
• Bête noire (French for "black beast," a person or thing strongly disliked)

The best synonym to use will depend on the specific context and the nature of the opposition. For example, in a sports match, "opponent" or "rival" might be appropriate, while in a story, "enemy" or "adversary" might be more fitting.