Sasuke Uchiha

When he was a child, he used to be a very kind boy, loving towards his parents and brother, and respectful to his clansmen and teachers. He was even very proud to being Itachi's brother and Fugaku's son, the ones who protect Konoha, and he always wanted to become like them. After Itachi massacred the clan, Sasuke's ideals and personality changed, becoming cold, lonely, and devoting his entire life to kill Itachi.

When first introduced to Team Kakashi, Sasuke displayed great indifference to his teammates. Feeling superior to all of them, including his teacher, Sasuke was unwilling to cooperate with Naruto Uzumaki or Sakura Haruno, as he felt they would provide him no aid in killing Itachi. However overtime, as he spent more time with his team, Sasuke began to lose some of his anger, caring more about his team than his revenge. To help push him back into his desire for power Orochimaru branded Sasuke with the Cursed Seal of Heaven during the Chūnin Exams to give him a taste of power. Although Kakashi Hatake sealed the Cursed Seal, Sasuke began to draw more power from it in the hopes of getting stronger.

According to Kakashi, Sasuke has both a superiority and inferiority complex, as he is unwilling to acknowledge when someone is stronger than him, but obsesses when he believes someone is stronger than him. For example, he was complacent with his rivalry with Naruto when he believed he was stronger, but when he noticed Naruto's fast growth, coupled with his defeat of Sunagakure's jinchūriki Gaara where Sasuke was beaten, and his quick defeat by Itachi on his return to Konoha led Sasuke to believe that his progression at Konoha was far to slow which lead to his defection to Otogakure. Upon defected from the village, Sasuke defected with the Sound Four and traveled to the Land of Sound, only to lose the entire Sound Four to the Sasuke Retrieval Team and face Naruto alone at the Valley of the End, where Naruto attempted to save him from his path of revenge. Sasuke in turn planned to kill Naruto, his closest friend, to awaken his Mangekyō Sharingan but upon his victory chose against it, instead vowing to beat Itachi his own way.

In Part II, Sasuke's personality remained largely the same, although his revenge against Itachi took precedence above all else, including his own life. He also claimed to have cut all ties to his life in Konohagakure, believing that they was the cause of his weakness, going as far as attempting to kill Naruto ,whom he spared in their previous battle, to prove how detached he was. However when he felt he had grown stronger than Orochimaru, he saw sacrificing his body to someone weaker than him was insulting to the Uchiha, and proceeded to battle and absorb Orochimaru's conciseness when the latter attempted to steal his body. Despite this, Sasuke seemed unwilling to needlessly kill in his quest for revenge[4], and later when battling Killer Bee and the Eight-Tailed Giant Ox, Sasuke remembered Team Kakashi after witnessing his own team Taka each sacrificing themselves to help him.

After his battle with Itachi, followed by his death and the revelation that Itachi was ordered by the Konoha Elders to kill the Uchiha clan and that Itachi truly loved him, Sasuke vowed to destroy Konoha to the last child for sacrificing Itachi and the Uchiha clan for their own happiness. With his new path of revenge, Sasuke had grown much crueler and more ruthless, killing anyone who stood in his way and sacrificing his own team to accomplish his goals. He had also shown great rage when someone speaks of Itachi in a negative way, crushing Danzō with his Susanoo for speaking ill of his brother.

Also, for his entire life, despite being popular towards females due to being handsome and cool, Sasuke showed absolutely no interest in any of these women, nor their advances, due to his only desire being for revenge and power. Such girls include Sakura Haruno, Ino Yamanaka, Karin, and even Mei Terumī; the Fifth Mizukage. Even when Sakura's childish crush turned to sincere affection, Sasuke still did not return the feelings, though before he left the village, he gave Sakura a genuine thank-you.