The Traitor

Top 10 Anim-- no. Just no.

The one who betrays their allies and joins the enemy side. The Traitor is likely one of the story's former protagonists to make things more dramatic. The Traitor can have their reasons to betray who they do. Such reasons can be that their allies suck, the other side is better, both, or they were coaxed into joining by somebody on the enemy side. If the Traitor is especially valued by the side they leave (be it for their strength, companionship, skills...), that side will make their best attempt to get their ally back from the other side however they can.

The Traitor's Mirrors
Nutshell: The one who switches from one side to another.

Enhanced: The one who temporarily switches sides to act as a spy on the other side for their allies. Shift: The Spy.

Cruel: The one who switches sides, temporarily or permanently, to get revenge on their allies for what they've done with the aid of their former enemies.

Inverse: The Loyal.

Up: Despite being betrayed, the Traitor's team still forgives their traitor of an ally and welcome them back to the team.

Down: The Traitor becomes Forever The Enemy's, never to return to their real friends.

Back: The "Traitor" was initially a friend of the enemy who left them and joined our Good Guys for whatever provided reason. Later, they return to their original friends and seemingly betray the Good Guys.

Forward: No mirror.

Atypical: This character could've been kidnapped by their enemies and forced to work for them using many methods (brainwashing, hypnotism, kidnapping...).

Wrong: This character betrays their allies only to return to their side soon after.