You don't need reapers to turn someone into a killing machine.

[In a literal sense, there's Bucky, the metal-armed assassin with the vaguest idea of a memory. Then there are the warriors, those who by necessity became machines. It doesn't take an alien to erase everything. It takes repetition and desperation to strip someone clean of themselves.]

I'd tell you I don't know if I can do this, but you'd tell me I'd have to do it, just like Erik told me. I've never killed anyone. I just don't want to be so shocked I can't do anything after that.