He kills Sasuke and Naruto with a single punch from his forbidden taijutsu known as Kyūkyoku no shi no ken. He further evolves the Rinnegan and Eternal Mangekyou Sharingan by combining them into the ultimate ocular jutsu known as Nishukangan. He is a rogue ninja that successfully resets the universe with his new
Steven Uchiha in his younger years
ocular jutsu. Upon resetting the universe, Robert Uzumaki came into existence as the new Sage of Six Paths and fought Steven Uchiha. Robert's Single Frame Hand Seal Style proved to be on par with Steven Uchiha's powers. The result of the battle brought existence to the New Konohagakure. Steven Uchiha's location and status is unknown. He is presumed to be dead but signs of his existence continue to show among the Naruto universe. He was known to possess the Sublime Reality of the Infinite Realms Style which allows him ultimate control of the fabric of reality and the infinite parallel realms.
Steven Uchiha with the awoken Nishukangan (Shippuden)
Along with his Nishukangan, he is simultaneously existing in all realms at once while not existing at all. He can be seen in Episode 186 of the original Naruto anime and Episode 377 of Naruto Shippuden. Though he was not seen at all in the 4th Great Ninja Wars,this was due to him singlehandedly winning the other Great Ninja Wars in the other infinite realms.
Last known appearance of Steven Uchiha
Robert Uzumaki performing his signature Single Frame Hand Seal Style