The Uchiha clan's Curse of Hatred has been referenced throughout the Naruto franchise and is often linked with stubbornness, a lust for power and deep-rooted goals exhibited by many of its members. When a member of the Uchiha clan is overcome by intense grief or sorrow, it releases a type of chakra in their optical nerves, activating their Sharingan.
Tobirama Senju, the Second Hokage, states that the Uchiha can feel the most love, making them capable of experiencing the deepest pain. These intense emotions lead them down a path of rage and hatred, manifesting differently depending on the Uchiha and their goals -- resulting in terrifyingly powerful shinobi like Madara. But what exactly is the Curse of Hatred?
The Curse dates back to when the Sage of Six Paths was on his deathbed, addressing his two sons -- Indra and Asura Otsutsuki -- to choose who could carry on his legacy. He ultimately chose Asura, who believed that peace could be achieved through love, instead of Indra, who valued power. Overcome by rage and jealousy, Indra gave in to Black Zetsu's temptations and waged war on his brother, eventually becoming the first person to awaken the Mangekyo Sharingan.
The Sharingan is a Kekkei Genkai unique only to the Uchiha clan and grants the user a great power tied to a deep emotional connection. The Mangekyo is a rare extension of this ability only seen in a select few Uchiha and requires an emotional trauma similar to losing a loved one to unlock. This cycle painfully repeats itself throughout the entire series. For Obito, that moment was watching his friend Kakashi Hatake reluctantly kill Rin Nohara, Itachi's was Shisui's suicide and Sasuke's was Itachi's death.
Even with their Kekkei Genkai, the Uchiha grew stronger through hard work and talent after unlocking their dojutsu. The intense pain and negative emotions that enable these abilities seem to strengthen with profound tragedy, and when you consider that aspect, the Curse of Hatred starts to become apparent. The powers of the Uchiha sets them up for hatred and despair from the beginning. Every shinobi wants to grow stronger, but for the Uchiha, the history of tragedy -- and philosophies of Indra -- put them down a dark path to unlock their true potential.
Sasuke is the most prominent victim of this Curse by bearing his entire clan's hatred after they are slaughtered. All of that hatred led him to crave vengeance and destruction until he completely lost sight of who he was.
The Curse of Hatred is also a direct contrast to Konoha's Will of Fire, derived from Asura's love-leading beliefs. The Will of Fire is an ideal rooted in loyalty and love, encouraging the villagers to remain hopeful and resilient through hardships, capable of being passed down through the generations. It values selflessness, whereas the Curse promotes the sacrifice of many for the betterment of a few. While the effects of the Curse of Hatred are seen consistently in Sasuke's character -- Indra's reincarnation -- the Will of Fire is actively present in Naruto Uzumaki -- Asura's reincarnation.
Luckily, a few Uchiha were known for breaking the Curse of Hatred and acting on the Will of Fire instead, including Kagami, Itachi and Shisui, who showcased a strong loyalty to Konoha. Others, like Obito and Sasuke, lost themselves to the Curse but found their way back eventually. All those cases prove the Curse is an obstacle that can be overcome by choosing to fight for others' sake and embracing genuine bonds instead of isolating oneself.
Sasuke and his daughter Sarada are the last remaining members of the Uchiha clan, and because of that, Sarada's circumstances are wholly different from her ancestors. With no influence to consider the Curse of Hatred and her goal of becoming Hokage and abiding by the Will of Fire, Sarada could set the fallen clan on a new path. Still, the tragic requirements of the Sharingan remain, and while she continues to fight for her comrades and the benefit of the village, it is unknown if there are other ways to unlock the full potential of her Kekkei Genkai.