Sasuke Uchiha is one of the strongest known characters in Masashi Kishimoto's Naruto series. Born a genius of the Uchiha clan, Sasuke was destined for greatness from a very young age and by adulthood, he managed to fulfill his potential and become a shinobi renowned as a hero for helping turn the tides in the Fourth Great Ninja War. By the end of the war, Sasuke was regarded to be one of the two strongest characters alive, with Naruto Uzumaki being the only one stronger than him.
Even though the main Naruto story ended there, Sasuke's quest to grow stronger certainly did not. Towards the end of Naruto, Sasuke was seen leaving Konohagakure to see the world through his own eyes and redeem himself while he was at it. This journey of his saw him get much stronger than he was during the Fourth Great Ninja War, even though fans never got to see it.
Sasuke Vs. Madara: Who Is Naruto’s Strongest Uchiha?
Sasuke continued his travels across the globe after the end of the Naruto series and, just like Naruto, was actively fighting during this time. While fans didn't get to see much of him during this time, it is a given that Sasuke's control over his Rinnegan increased several times during these few years. It is important to remember that Sasuke received the Rinnegan on the last day of the Fourth Great Ninja War. While he was skilled enough to make use of it, Sasuke's efficiency with it was far from what one would explain expect of a Rinnegan master.
During his fight against Naruto, Sasuke commented on how his control over the eye was improving and that he was finally getting used to it, implying that during his fights against Madara Uchiha and Kaguya Otsutsuki, Sasuke wasn't even at his strongest. With that established, it is quite easy
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