Dinosaurs on a Spaceship - S7-E3
Revealing mistake: The Doctor tells everyone to run, which they do. As they go around a corner in the distance, the actors at the rear of the group, presumably believing themselves out of shot, slow to a trot. (00:05:04)
Chosen answer: The Master knows that deep down, he deserves death for the crimes that he's committed throughout his life, and since he regards The Doctor as his arch-foe, he expects it to be at his hands. The fact that The Doctor is still willing to forgive him for all of his crimes hurts him more deeply than death would.
Captain Defenestrator