Akihiko Kayaba
Akihiko Kayaba is the Director and Creator of the Nerve Gear and Sword Art Online. He traps all the players within Sword Art Online by using the Nerve Gear to cease sending signals to the users' body. Any attempt at removal, loss of power for a certain period, or if the user dies in the game will also kill the user. His motivation is to observe what happens after he traps them.
He is in fact Heathcliff in the game SAO, who is the leader of the guild Knights of Blood. This was found out and revealed by Kirito after the defeating of the boss on the 75th floor. Because of this, he offered Kirito a chance to beat him in the duel with the condition that if Heathcliff is defeated, the remaining players will be able to log out. After a fight in which it appears both Kirito and Asuna are defeated and killed, Kirito, with his final efforts, managed to use Asuna's rapier and stab Heathcliff through the chest thus defeating him and clearing the game.
It was later revealed that neither Kirito nor Asuna died and in the final moments of the game Heathcliff personally congratulated Kirito on winning the game, saying that he was the one he had an eye on from the beginning due to his amazing reflexes and reaction time which granted him the use of