I very much doubt that the power the Dark Lord knows not is ambition. See: chapter 70.
I'm throwing Quirrell's very words from that chapter in his face :). It doesn't sound like he has a clear idea of what to do with the world after he achieves domination of it.
If Harry can't quite say in Parseltongue that the Dark Lord has no ambition, he can nevertheless be confident that the particular ambition of discovering the magical theory of everything is unique to HJPEV. I think it's reasonable to call this his true hidden power, as it's the meta-power behind his invention of partial transfiguration, and a key ingredient in his power over Dementors (expecting death to be solvable). I suspect his honest answer to whether V would ever discover this ambition is that he doesn't know.
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: