The main character is the protagonist, so his opponent is the antagonist.
No, the protagonist is almost always the main character (but not always). And it is true that he can be in conflict with himself (inner doubts, fears, duty-bound etc) but most often it is the antagonist that is in conflict with the main character.
No, the main character is typically the protagonist of a story. The protagonist is usually the central figure who drives the plot forward and is involved in the main conflict. The antagonist is the character who opposes or creates conflict for the protagonist.
the antagonist
The main character having the conflict is called the protagonist.
Antagonist
antagonist
A main conflict is the main problem that a character has in a story, or the main problem of the story
antagonist
It may be between different characters (basic "good guy-bad guy" scenario) or between a character and a situation or even within a character himself/herself. Conflict always leads to a Crisis. So basically like the main problem or something like that.
External conflict
Paul learns that adults are not perfect. He learns that perfect and fair do not always exist. He also learns how he lost his sight.
The word "protagonist" means first combatant or the primary individual involved in a conflict.