1. Obito Uchiha
Obito Uchiha was a complicated character. He was good, then he turned evil. He started the Ninja War, and in the end realized his mistakes by watching the unwavering Naruto. He ended up giving his life for the next generation. Although Obito committed lots of mistakes, he eventually redeems himself by sacrificing his life.
Orochimaru was an S Rank criminal, because of how dangerous he was. He had some sort of grudge against Konoha, and he attacked it several times and even killed Lord Third. However, in the end, he realizes the error in his ways, and tries to observe the path that Sasuke chooses instead.
3. Kabuto Yakushi
Kabuto Yakushi lost his identity after Orochimaru’s death. He gained tremendous power in the wake of the 4th Great Ninja War, but he had no identity. He was set in the right path by Itachi Uchiha, who used Izanami on him. Kabuto later saved the life of Sasuke Uchiha.
4. Nagato Uzumaki
Nagato Uzumaki was a student of Jiraiya. He ended up killing his own sensei, and then he invaded Konoha. However, after he fought Naruto and lost, he was so loved by Naruto and his unwavering conviction to bring world peace, that he sacrificed his life for him and brought back the people he killed during the invasion.