Here's why:
* Protagonist: The main character of a story, often the hero or the one the audience is meant to sympathize with.
* Antagonist: The character who opposes the protagonist, often the villain or the one who creates conflict.
While "antagonist" is the most direct opposite, other words can be used depending on the context:
* Villain (if the antagonist is clearly evil)
* Opponent (more neutral, for any character who goes against the protagonist)
* Foil (a character who highlights the protagonist's traits by contrasting with them)
It's important to remember that these terms can be used in more complex ways, and the specific relationship between characters in a story can be nuanced.