Since tsunde-sama50 sent me a pm guess I have to reply to this. Of course his toughest fight was against Neji. Neji was the only person to force him into using Kyuubi without needing to see one of his friends in danger. I don't consider the Gaara fight that hard considering Sasuke did the hard part of getting Gaara to remove the sand shield, if Gaara was calm in a fight against Naruto he would've won. Naruto isn't fast enough to get through the sand wall.