He died and he used his haxor existence and somehow overcame the system and killed Heathcliff. Sort of like how Asuna broke through paralysis to protect Kirito. rofl.
Alright. The anime didn't make it clear but the reason why that penultimate sequence, with Asuna and Kirito was done the way it was is because they both thought they were going to die. In reality, they did die in the game and as a result they would die. The only reason they didn't die right away was because they thought Akihiko let them live a little longer so they could talk, being the winners and all, and such. Kirito was surprised that he woke up in the real world because he was under the assumption he was going to die. Like I said, the penultimate scene makes more sense if you're under the assumption that both the characters knew they were going to die.