What episode Sasuke turn evil?
From the first show Naruto in season 1, episode 29, the snake that bit sasuke in the neck made a mark of evil, soon he was gonna release or seal the snake power.
Why did Sasuke turn into a villain?
However, the desire of revenge and manipulation of Tobi made Sasuke into a major villain. In the finale, he became the final villain of the series due to his belief the only way to change the ninja world is through a revolution by murdering the five Kage, before redeeming himself.
Is Sasuke a villain now?
He is a rival of the titular protagonist Naruto Uzumaki. Despite being the overall deuteragonist of the series, the desire for revenge and the manipulation of Orochimaru and later Tobi made Sasuke into the main anti-villainous antagonist of both the middle of Part I and the whole of Part II.