Dalek Caan

Dalek Caan, although eventually the betrayer of Sec, is a visionary in his own right. He is the last member of the Cult alive and he engineers the destruction of his own race after he attempts to enter the Time War, which was Timelocked by Dialga. Caan's Passage of Time was shattered and he came face-to-face with a superior being. Unable to comprehend this fact, Caan started to go insane.

Seeing him as a way to end the Imperial Daleks' meddling with Time, Dialga allowed Caan into the Time War to rescue Davros. Shortly after he showed Caan the vision of Time, which convinced him the Daleks were actually pretty evil and removed the last vestige of sanity. He went back to preach Dialga's word, but the Daleks were not willing to listen. Because of this, Caan lied to the Daleks by preaching about their supposed invincibility, which led to their deaths at the hands of the Reality Bomb.