I hate Sasuke because of how weak willed he is and how he doesn't love up to his own hype. He changes his kind at the drop of a hat, has been swayed by Itachi, Orochimaru, Obito, used, and has no honor. I respected him in Part 1 but now he's just being an entitled little drama queen and thinks his pain is greater than everyone else's.
And he's supposed to be a genius, but he gets rolled by Deidara, Ay, Killer Bee, Ohnoki, and only beat Itachi because he let him. Then he attacked Madara out of turn twice and paid both times.
But, that's just me. I officially hated him when he thought slaughtering innocent people was justifiable for his butthurt.