Rusty (Into the Dalek)

"Rusty" was the name given by the Twelfth Doctor to a Dalek that was captured by the forces of Combined Galactic Resistance. Voicing its belief that the Daleks needed to be exterminated, "Rusty" was investigated by the Doctor, to see if it was possible to exist a 'good Dalek'. (TV: Into the Dalek)