Doctor Who: 10 Times The Doctor Was The Bad Guy

In Donna Noble's first adventure with the Doctor, she saves his life, solidifying her place in his history. While her actions were heroic, they were a stark contrast to the actions of the Doctor himself, who was ready to stand-by and watch the last of an ancient race drown.

The Racknoss, while a deadly foe, were all but extinct when the Doctor encountered them. The Empress herself was hiding away on her ship, though her children were sleeping at Earth's core, ready for her to wake them and bring them up to the surface. Thanks to Donna, the Doctor was able to discover this plan and set about stopping it.

He began to drain the Thames River into the shaft that had been burrowed into the Earth's core. So far, so good. The Empress arrived, engaging the Doctor in battle. Then, the true hard-hearts of the Doctor emerged. Using little bombs in the shape of flying Christmas baubles (just go with it) he began to attack the Empress, watching her scream in agony and despair as her children drowned.

The events of Turn Left proved that, without Donna, the Doctor would have stood there watching the Racknoss die. Though that would have led to his own death, it was another example of the Doctor losing himself in destruction.