This is more of an opinion thing. In my story, the antagonist will most likely die. But, there are so many characters that could be candidates for that. In a sense, a lot of people have a bone to pick with this guy. Please just tell me which option you'd find most effective. 1: Love interest kills him. She is a master strategist, and although she really DOES love him, she knows that it would be more advantagous to have him eliminated. 2: Chekhov's Gun kills him. For those of you who are unfamiliar with the term, this character is a princess who is mentioned simply and without much delving into early in the story, until she comes back in the end to finish the antagonist off. Good for surprise. 3: Protagonist kills him. This option is included because it would give the best sense of conflict resolution. To rephrase this, which endings do you most prefer: ones that make you think, ones that surprise you, or ones you find satisfying?