Sasuke was a happy child, eager to please and be worthy of his family name.This changed after his entire family was killed by Itachi, the person he most admired in the world. He became cold toward others, unmoved by and uninterested in what they do or think of him, choosing instead to keep to himself. He stopped using honourifics like “sensei” or “sama“, something considered rude in the Japanese language. His only goal in life became to take revenge for his family’s deaths and, by extension, acquire the power needed for that revenge, even if it meant acquiring an external power that wasn’t his own.
The pursuit of power, difficult enough on its own, is something that Sasuke repeatedly struggles with. Whenever he meets new people, he makes an evaluation of their abilities: those he perceives to be weaker than himself he arrogantly disregards, giving them as little attention as possible so that they won’t hold him back; those he perceives as stronger he fixates over and tries to surpass, especially when he believes he should be their equal. As a member of Team 7 he is repeatedly exposed to Kakashi Hatake‘s philosophy that there is strength in teamwork. For a time, Sasuke accepts this, experiencing it first-hand on several of Team 7’s missions. He even starts becoming attached to his team-mates and starts to forget the vengeance he craved. But when he meets Itachi again in Part I and is summarily defeated, Sasuke decides the team is making him weak and chooses to leave them and Konoha entirely, focusing solely on himself.
Prior to Sasuke’s defection, Kakashi tries to point out the contradiction in Sasuke’s viewpoint: he is driven to gain power because he lost his family, yet sacrifices the family he still has (Team 7) in order to gain that power. In Part II, Sasuke allows Orochimaru to experiment on him as long as he becomes stronger, only to turn against Orochimaru for using him in the first place and acquires new teammates with abilities that could further his goals. Sasuke initially set a no-kill policy for himself and his team against those unrelated to his revenge. This was dropped as his hatred increased: at the Kage Summit, he slaughtered numerous samurai in cold blood and recklessly challenged the five Kage before killing Danzō Shimura; he tries to kill Karin and Team 7 when they impede or attempt to dissuade him from his objectives; he allies with Tobi and Akatsuki when their goals align, but leaves them without comment when he no longer needs them. His abandonment of all his former loyalties and his criminal acts convince his former classmates that Sasuke is beyond salvation.
After his final encounter with Itachi, Sasuke is left uncertain about what course to take; Orochimaru hypothesises this indecision is due to Sasuke, for the first time, being without anybody to tell him what to do. From long contemplation, Sasuke decides that the desire for retribution that drove him for so long is the perfect solution to the world’s problems: if a single individual, what Sasuke calls the “Hokage“, is solely responsible for making the difficult decisions, killing and the like for the greater good, then everybody will be unified in their hatred of that individual. He volunteers himself for that responsibility and, in order to prepare himself, plans to eliminate what few friendships he still has, namely Naruto. But Naruto, by refusing to give up on saving Sasuke from darkness, demonstrates that their friendship is too fundamental to who Sasuke is and that it cannot nor should it be broken. On coming to terms with this, Sasuke stops fighting the many bonds he’s made and chooses to die so the Curse of Hatred would die along with him. However, after further convincing from Naruto, Sasuke chose to live to find redemption instead.
One of Sasuke’s most significant bonds is the one he has with his older brother, Itachi, who by merely being mentioned can elicit strong reactions from Sasuke’s otherwise calm demeanour. Sasuke adored Itachi when he was a boy, enjoying his company above all others’; as an infant, he would cry whenever he was held by someone besides Itachi and immediately be happy once held by his big brother again. When Itachi murdered the rest of the Uchiha clan, Sasuke was crushed not only by the loss of his family but also by what Itachi told him: that he had never loved Sasuke. Sasuke devotes years of his life to avenging their family by killing Itachi, which Itachi encourages whenever they meet. Sasuke is accordingly careful not to follow Itachi’s instructions too closely, such as by not acquiring a Mangekyō Sharingan, as he doesn’t want Itachi to have the satisfaction. After Itachi dies in battle with Sasuke, however, Sasuke learns that the hateful older brother that Itachi seemed to be was an act and that, in truth, Sasuke was the most precious person to Itachi; his murder of the Uchiha was done on instructions of Konoha, in order to protect Sasuke. Sasuke becomes overwhelmed by this discovery and starts conspiring against Konoha and all its citizens for ruining his and Itachi’s lives, knowing full well it isn’t what Itachi would want him to do. He changes his mind after he is able to speak to a reincarnated Itachi, adopting some of Itachi’s views: he decides to fight for Konoha’s future so that Itachi’s actions aren’t made meaningless and bases his understanding of the “Hokage” around the decisions Itachi made. He also starts poking the foreheads of others as a sign of affection, something Itachi used to always do with him.
Sasuke first met Sakura Haruno when they were children in the Academy, where his good looks caused her to become infatuated with him, which later grew into love. On his part, Sasuke was aware Sakura had feelings for him, but he showed no interest in her and considered her to be annoying. After they became team-mates, they began to interact more and acknowledge each other’s strengths and weaknesses, causing Sasuke to think of her as someone he needs to protect. Despite feeling grateful of how much she is willing to do to make him happy, he still abandons the prospect of being with her to pursue revenge and defect Konoha. By the time the Fourth Shinobi World War gets underway, Sasuke had becomes so consumed with hatred that he was willing to kill Sakura, who had never given up on bringing him back home but was left devastated of how cruel he had become. After the war, a redeemed Sasuke apologizes to Sakura for how much he hurt her and she tearfully forgives him, allowing them to reconcile. They later maintain a long distant relationship while he pursues a journey of redemption. Sasuke was indecisive of whether to settle in Konoha until he learns from Naruto’s letter that Sakura never lost faith in him, causing him to return to the village. They later marry and have a daughter, Sarada. As a father, Sasuke seems to be a loving and doting one, as he can never bear to see Sarada sad and is willing to do anything to make her happy. However, Sasuke tends to be emotionally distant with his family for the sake of his duties, though he feels a strong connection to them when they are apart. Sasuke loves his daughter dearly, as he puts her safety before his own, and promises her to come home before returning on his traveling. While Sasuke is happy in his marriage to Sakura, he enjoys teasing her by declining to show her affection.
During his time as a wanderer, Sasuke was a recluse, keeping contact with people to an absolute minimum and maintained his strong sense of pride; he is willing to help the villages if their problems are beyond their expertise but ignores their requests if facing insignificant issues. He also sometimes act independently on his own and helps the five nations, but does not even bother to interact with anyone during such instances, although he does leave strong hints he was responsible. Acknowledging his mistakes and once free from hate and vengeance, Sasuke reverts back to the type of person he was prior to the massacre; being kind to others and displaying a sense of humour but maintaining his aloof exterior. Although publicly regarded as a hero for his role in the war, Sasuke feels that his crimes and imperfections out weigh anything heroic he has ever done.
As an adult, Sasuke becomes wiser and mature, as well as genuinely warm and caring, although he retains his habit of insulting others, albeit more comically than coldly. Although he fulfils Itachi’s wish for him to live and protect Konoha, his duty of protecting it from the shadows and investigating the mysteries of Kaguya leave Sasuke unable to spend time with his family, to the point where he failed to recognise his daughter Sarada. Sasuke takes his duties as a shinobi and a father seriously: he spends most of his daughter’s childhood investigating threats greater than Kaguya; he is protective of Sarada and is very supportive of her goal to become Hokage and not end up like him. Sasuke admits his mistakes as a father, but he has strong parenting skills, as he has faith in Sarada’s abilities. Nevertheless, Sasuke loves his family dearly, as he tries to spend time with them when he is able to come home, and expresses pride in his daughter’s growth and achievements.