An antagonist is the "bad guy" in the story, and usually fights against the protagonist ("good guy").
Based on the answer choices, the one that describes an antagonist is:
1) An evil henchman who kidnaps the country's favorite princess
The wording says he is "evil" and he also kidnapped a good person in the story, because she is the country's "favorite" princess. This causes conflict, which is what the antagonist usually creates/causes.
The other options describe protagonists or others that have little to do with the story.