Death Eater
Snape is generally depicted as being cold, calculating, precise, sarcastic, and bitter. He strongly dislikes Harry and often insults him by insulting his father James. As the series progresses, it is revealed that his treatment of Harry stems from Snape's bitter rivalry with James when they were in school together. In particular, James and Sirius bullied Snape, which according to Alan Rickman caused the already lonely boy to further "shut himself in". Rowling further described the young Snape as insecure and vulnerable: "Given his time over again [Snape] would not have become a Death Eater, but like many insecure, vulnerable people he craved membership of something big and powerful, something impressive.[...] [He] was so blinded by his attraction to the dark side he thought [Lily] would find him impressive if he became a real Death Eater."