Originally Posted by
Jason
Well, not really in the books. Snape there is an antagonist because he actively bullies students that do not belong to his favored house, like poor Neville, and promotes his favored students, like Draco Malfoy, at every opportunity. He is actively malicious, not just someone trying to follow the rules.
He hates Harry from the first sight of him. Later he also resents him for getting away with constant rulebreaking, but he was determined to never like Harry Potter, the son of his hated enemy and rival James, from the start.
That said, he is not a villain. He hates Harry and would love to see him be expelled, but he also saves his life on many occasions (and occasionally vice versa) and eventually accepts that Harry is necessary to defeating Voldemort.