I thought about that too, however, the Doctor refers to him as his big secret. But everyone knows the Doctor was involved in the Time War, and at least somewhat know what he did (he was the one who locked Gallifrey and the Daleks away, cutting the war off from the rest of time and essentially destroying them), so it's not much of a secret.
Ah, but what
else did he do in the Time War?
"The Cruel Tyrant. The Slaughterer of the Ten Billion (Worlds? Star systems?
Galaxies?!?). The Final Darkness."
Eleven's words (do we start putting quotes in there now? 'Eleven'?) seem to spell out that Hurt's Doctor did some - no, a LOT - of f'd up, totally-against-character, flat out EVIL things before Gallifrey went boom. And it was
only when he had to pull the trigger on his own planet - his own people - that he was shocked back to the side of "peace and sanity."
This is the Doctor that went to the Dark Side.