The Six

The Six was the main alias used by the sixth incarnation of a Renegade Time Lord who suffered from regenerative dissonance.

The Six was extremely violent and also very unstable. He would often try to get his future incarnations to butcher their way through a situation, regardless of whether the victims could be of use. (AUDIO: The Eleven, Companion Piece)

When the Twelve tapped into her old personalities, the Six threatened her and the Doctor. The Twelve made her old incarnation apologise, and described him as a "horrible little man", while the Doctor said him to be a psychopath. (AUDIO: Planet of the Ogrons)

When Liv called the Nine a psychopath, he corrected her, saying that he was a kleptomaniac, and the psychopath was "three regenerations back".

Angered by River Song's plan of escaping, the Nine considered letting the Six "off the leash". He found the Nine's torture of River, Liv, Helen, Charley and Bliss to be "fun". (AUDIO: Companion Piece)