Amarande: An instructive example of "playing heedlessly in aggressive mode without consideration for changes of fortune leads to disaster."
Here White continued to play as if he had the advantage, while after 12 ... Qxc6 it would appear that he has none, and that it has even passed slightly to Black, with his two Bishops and the long diagonal pressure characteristic of the Dragon. (White's c3 knight clearly has to vacate the premises, after which the b2 pawn will be under fire; White will have to play either c3 or Rb1, neither of them especially rosy, in order to develop the Bishop)
It would probably have been better for White to exchange the Knights on move 13, the entire game shows how dangerous Black's Ne4 is - not only did it deliver the mate in the end, but its potentiality to sacrifice itself at g3 to unblock the long diagonal for Qxg2# is a salient theme throughout. Indeed it becomes almost immediately troublesome, e.g. White is forced to block his Bishop's development with 15 Ne3 as 15 Nb4? would allow ... Ng3+! and mate next move.
Despite this, White continues to play aggressively, even when there are no obvious targets of attack, and in a corr game there is much less advantage to mixing it up as the opponent has leisure to evaluate the complications.
17 f5 (and the subsequent virtually forced fxg6) can probably be forgiven, as strategically Pf4 interferes with White's Bishop's development after the Knight can leave e3, but 21 Nh6+?? is definitely faulty and loses the game at once (21 Nf2 was much more to the point, by this point the Bg7's immediate strength has greatly diminished, while the Ne4 still has a choking effect).
After 22 ... Qh3 it is obvious that mate can only be prevented at the cost of a piece.