The Doctor succumbs to the hurt doctor and goes around doing bad shit in the name of peace like sacrificing millions of children for the sake of the world.

Or going to pompii to make sure his past self destroys it so the pyrovillians don’t burn the world by killing an entire city.

Eventually, he shoots himself in the head but he’s used up all 13 regenerations (because of tennants half regeneration that resulted in 10.5)