Doctor Who: Every Version Of The Doctor Explained
8. The War Doctor (First Appearance: 2013)
The War Doctor was who the Eighth Doctor chose to regenerate into during the Time War. He committed many dark acts, including pressing the button that destroyed Gallifrey and the Daleks on the final day of the battle.
In The Day of the Doctor, his successors feared the War Doctor at first, but soon realised they actually had a lot in common, and that there was a soft centre beneath his grizzled, battered exterior.
The rehabilitation of the War Doctor – and the three Doctors reconciling their dark past – is at the core of Doctor Who's 50th anniversary special, and it's lent real emotional heft by the casting of the late John Hurt.
After he saved Gallifrey with his past and future selves, the War Doctor's body couldn't take much more, and he regenerated into the Ninth Doctor.