Indeed, the only obvious “power” Harry has that is (as far as we know) unique to him is Partial Transfiguration. I’m not sure if Voldie “knows it not”; as someone mentioned last chapter, Harry used it to cut trees when he had his angry outburst in the Forbidden Forest, and in Azkhaban as well. In the first case Voldie was nearby, allegedly to watch out for Harry, but far enough that to be undetectable via their bond, so it’s possible he didn’t see what exact technique Harry used. In Azkhaban as well he was allegedly unconscious.
I can’t tell if he could have deduced the technique only by examining the results. (At least for the forest occasion he could have made time to examine the scene carefully, and I imagine that given the circumstances he’d have been very interested to look into anything unusual Harry seemed to be able to do.)
On the plus side, Harry performed PT by essentially knowing that objects don’t exist; so it could well be possible to transfigure a thin slice of thread of air into something strong enough to cut. For that matter, that “illusion of objects” thing should allow a sort of “reverse-Partial” transfiguration, i.e. transfigure (parts of) many objects into a single thing. Sort of like what he did to the troll’s head, but applied simultaneously to a slice of air, wands, and Death Eaters. Dumbledore explicitly considers it as a candidate against Voldemort (hint, Minerva remembers Dumbledore using transfiguration in combat). And, interestingly, it’s a wordless spell (I’m not even sure if Harry can cast anything* else wordlessly), and Harry wouldn’t need to raise his wand, or even move at all, to cast it on air (or on the time-space continuum, or world wave-function, whatever).
On the minus side, I’m not sure if he could do it fast enough to kill the Death Eaters before he’s stopped. He did get lots of transfiguration training, and using it in anger in the forest suggests he can do it pretty fast, but he is watched, and IIRC transfiguration is not instantaneous. He probably can’t cast it on Voldie nor on his wand, though he might be able to destroy the gun. And Voldemort can certainly find lots of ways to kill him without magic or touching him directly; hell, he probably knows kung fu and such. And even if Harry managed to kill this body, he’d have to find a way to get rid of the Horcruxes. (I still don’t understand exactly what the deal is with those. Would breaking the Resurrection Stone help?)
thin slice of thread of air
It has been established that air can't be Transfigured due to the constant motion of its particles; they don't hold still long enough for you to Transfigure them.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 113.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)
IMPORTANT -- From the end of chapter 113: