Sasuke, Gaara, Naruto (all jins to be exact), Kakashi, Obito, Nagato, Iruka, Madara, Hashirama, Orochimaru, Tobirama, Itachi, Lee, Neji and some more others had it tough.
kabuto because he had his family killed in a battle and then after finally being accepted somewhere else and making a new family he has to leave with root which is crappy an even crappier childhood and then after his training he had to spy on different countries where he obviously made connections with people sense its impossible to spend so much time with people and not make a friend and after that he was forced to betray them and then near the end of his "childhood" he was forced to kill his "mother" he easily takes this