The War Doctor (John Hurt)
Originally young and robust, the War Doctor, played by John Hurt, set upon the warrior path for which he had been intended, and disavowed the name of “the Doctor”. Though the Time Lords and Daleks continued to refer to him by that name, he was also referred to as “the Renegade” by Lady Priyan and “the Warrior” by Clara Oswald.
After becoming old and tired of battle and faced with the end of reality, the Doctor considered activating the Moment, to end the Time War by committing genocide against both the Daleks and his own people. However, the Moment’s sentient interface led him down a different path by letting him view his future first-hand. By teaming up with his later selves, his mind was opened to a heroic way to end the Time War in lieu of the deadly alternative he was going to enact.
Knowing he could unite with former and future Doctors in force, the War Doctor helped to save Gallifrey from destruction, although he was not able to retain these memories. Because of this, his later incarnations disowned him, believing him to have destroyed Gallifrey. Only the Eleventh Doctor retained the memories, and eventually remembered him as the man who saved Gallifrey, restoring the War Doctor as an embraced and respected incarnation.
After battling in the Last Great Time War for a remarkably long time, this incarnation eventually regenerated into a younger form due to advanced old age after he had helped save Gallifrey and reclaimed his name.