The Doctor looks out from the TARDIS over the planet he's loved for thousands of years.
The earth is a desolate rock, a nuclear waste land with not a single thing left living.
He tried. He really did. This time is was just too much for him, he couldn't save everybody. Hell he couldn't save anybody.
The one thing he couldn't stop, had absolutely nothing to do with aliens, it was all humanity's doing.
It was inevitable he supposed that the beautiful planet would die like this, murdered along with billions of innocents by the power of a few angry humans with too much power trying to outdo each other.
He didn't have the heart to look at his surrogate home for another second and so with a snap of his fingers and the flip of a switch he was off to the unknown.