Pain...before his change. First he stomps Jiraiya by breaking his throat, stabbing him multiple time and having his corpse rotting deep down a river. Then he goes to Konoha and kills dozen's of random ninjas, put's Chouza in a near death state, kill's Kakashi with a little nail, rips out Shizune's soul for the hell of it, flattens Konoha village because Tsunade disagreed with him, murders Pa frog w/o much effort, chokeslams Naruto before stabbing him multiple times and even mocks him by having a casual chat in hostel territory. This gives him the opportunity to later humiliate an emotional Hinata and stabbing her to near death just to see if Naruto would feel a little 'pain'. Not sure what happens after that...