Question

Tom has hated Sam (main character) for a long time; he plans to seriously harm Sam, one way or another. In this scenario, Tom is the

Answer 1

I have answered this very same question this year. Tom would be the antagonist, since Sam is the main character, and the main character is always the protagonist, whether good or evil.
The answer is antagonist.

Answer 2

Antagonist = Bad
Protagonist = Good/ Main character