Neji. I never hated him, I just disliked what an arsehole he was. Even when he changed to a decent guy I still didn't care for him. Than one day I just started liking him.
I never disliked Lee himself. Shamed to say that his appearance made me steer myself away from him. But than his personality won me over.
Kankuro, an unpleasant idiot who kept bad-mouthing Konoha. I was so happy when he witnessed Naruto defeat Gaara he got his arse kicked by Shino, proving the strength of the Leaf village. But than I just grew to love him when the manga showed how dedicated to his brother he was.