Why is it said that Professor Severus Snape is a character with many layers?

Professor Severus Snape is an exceptionally skilled wizard whose coldly sarcastic and controlled exterior conceals deep emotions and anguish. Professor Snape is hostile to Harry due to the latter’s resemblance to his father James; James Potter had bullied Snape during their time at Hogwarts. Albus Dumbledore trusts Snape for reasons that are not disclosed to others. Snape’s loyalty is under question until the seventh book, in which his full story is revealed.

J K Rowling describes Snape as a ‘horrible teacher’ whose story she had visualised since the first book. Actor Alan Rickman portrayed Snape in all eight Harry Potter films, released between 2001 and 2011.

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