Even with Harry Potter author J.K. Rowling stating on record that Severus Snape was not a bad guy, some Harry Potter fans just cannot seem to warm to the potions master. ... These are clues throughout the Harry Potter movies that reveal Professor Snape was not the villain he was portrayed to be.

Did Snape really betray Dumbledore?

In return, Snape secretly allied himself with Dumbledore and the Order of the Phoenix as a double agent against Voldemort, using his powers of Occlumency to hide his betrayal from Voldemort. ... Even with his efforts to protect her, Snape felt responsible for Lily's death at Voldemort's hands.

Why did Severus Snape turn bad?

Snape as a person was not very friendly or social, for that matter. His anger had a lot to do with his troubled childhood. He was a halfblood, had parental issues and was thoroughly bullied by James and Sirius at Hogwarts. This led him to develop a tough exterior.