The Doctor: We can end this right now. We can save everyone right now.
Amy: This is not how we roll and you know it. What's happened to you, Doctor? When did killing someone become an option?
The Doctor: Jex has to answer for his crimes.
Amy: And what then? Are you going to hunt down everyone who's made a gun or bullet or a bomb?
The Doctor: But they keep coming back, don't you see? Every time I negotiate, I try to understand. Well, not today, no. Today I honor the victims first. His, the Master's, the Daleks', all the people who died because of my mercy.