So what you are saying is that Amon was defeated by deus ex machina because it took deus ex machina to move his defeating Mako from a room without a window to a room with. Or are you saying Korra airbent through his blood bending and that's the deus ex machina? Cause she didn't. Amon wasn't bloodbending her then because he thought her already debent. Or do you mean Korra gaining airbending at a crucial moment is the problem? Sure, maybe, but that's kind of weak.