The Three

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

Post-mortem
After finding out that Bliss was indeed a companion of the Doctor and that she would not be killed by the Nine, the Three complained about it, and was told that one could not always get what they want. (AUDIO: Companion Piece)

Personality
The Three, as noted by the Eighth Doctor, was one of the personalities more willing to kill. (AUDIO: The Eleven, Companion Piece)

Behind the scenes

 * The script of Dark Universe describes the Three as "a childish, playful self-centred persona, prone to petulant tantrums if crossed".