Sasuke Uchiha

Sasuke Uchiha is a complex character (let me make this short) Sasuke used to be lively child with big aspirations to be equal to his older brother Itachi. But Tragedy struck, when he saw his brother kill his whole clan. But he didn't exactly turn away form the village yet. He was on team 7 with Naruto Uzumaki, Sakura Haruno, and Kakashi Hatake. He even made a slight friendly bond with Naruto not like buddy-buddy but could rely on each other. Until he tried to find Naruto and he saw Itachi, he tried to kill him but got put into a genjustu where he relived seeing his parents die 1000 times. This carved his path to leaving the village to seek for power to make a revolution against the ninja world. Naruto and Sasuke had a fight at the final valley and yeah, then Shippuden. In Shippuden Sasuke was more cold, arrogant, detached, and very condescending. He was way different from before, before he was very emotionally conflicted and had hesitation to kill and hurt others. But in Shippuden he was world-class threat, killing off people like flies. When he first "Killed" Naruto (he didn't die) he was terrified and was trembling and coughing about to throw up, in Shippuden, He could care less if Naruto was dead. In mid Shippuden Sasuke Unlocked the Mangekyo Sharingan where he didn't really master it everytime he used it, it hurt. Despite Sasuke's one tracked goal his goal alters throughout the story, first wanting to just kill Itachi, to wanting to become Hokage of the leaf to change the ninja world, to wanting to kill off every Shinobi and completely rebuild the ninja world and becoming the "God" or Ruler of it with no Shinobi and corruption left. He also trained with Orochimaru which in short he is a freak. This is around the time he killed Itachi so you can make it before or after.