Continuity mistake: When Colonel Mace confronts Commander Skorr, he raises his gun twice; once in one shot, and immediately after in the other. (00:30:30)
Continuity mistake: Near the end, when Luke teleports and switches places with the Doctor on the Sontaran ship, Luke catches the atmospheric converter's switch twice, once in the wide shot and then again in his POV. (00:40:25)
Continuity mistake: When the Doctor activates the teleport, Donna is onboard the Sontaran ship, holding a cell phone in her left hand. When she arrives in the basement of the ATMOS factory, she's holding the rubber mallet in her left hand, and her right hand is empty, with the phone nowhere to be seen. (00:32:40)
Continuity mistake: When the Doctor pulls out a TARDIS key to give to Donna, the exact position of the key in his hand changes between shots. (00:05:00)
Continuity mistake: When Donna is sneaking around the Sontaran ship, she's carrying Martha's old phone, which she's using to stay in touch with the Doctor, and the rubber mallet from the TARDIS. There are times when one of the two objects, the phone more often, is missing from her hands with no explanation.
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