Lizuka
[spoiler]I thought the Pony of Shadows was by far the lamest main villain to date honestly. Guy basically just goes through the whole Riku subplot of Kingdom Hearts in like five minutes, had very flimsy reasons for his turn to the dark side (and really, rejected by his friends or not, responding with, "I'm going to join up with some ill-defined abomination and destroy the world!" renders him not very sympathetic regardless), and he didn't come off as actually menacing at all.[/spoiler]