Why Did Sasuke Turn Evil? Sasuke turns evil when he learns the Leaf Village forced Itachi to destroy the Uchiha clan. He received Orochimaru's curse mark which caused his escape from the village, but he did not become a truly evil person until he felt the need to defend his brother.

What episode does 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 betray Naruto?

As Naruto explains, Sasuke left because he wanted to gain power. The Uchiha Clan was annihilated, and he's been wanting to get revenge as the sole survivor. But Boruto's confused at this, so Naruto explains that Sasuke did it in order to sever all his bonds.