Sakura: I didn't mind part 1 Sakura and was actually positive about her. I kinda appreciated early part 2 Sakura but her character took a drastic turn after the Pain arc. I hated how she kept going after Sasuke, even when he tried to kill her. She was one of those stubborn characters who would go as far as leave their village/family/friends just for a one-sided love? That's bad writing to me. Yet, I thought that her character was redeemable. Now that the series has ended and her character has been put to a closure, I can assert that I hate her personality.
Obito: Hated how he took a 180 degrees turn. I respected him for his ideals and his unwavering conviction but at the end, Kishimoto turned his character into a fail.
Kaguya: So much potential wasted.