Izuna Uchiha
Izuna was Madara's younger brother and one of the most powerful members of the Uchiha clan during its early days, well before Konoha was even founded. He and Madara stood at the very top of the clan together.
What really set Izuna apart was that he was among the first Uchiha to awaken the Mangekyou Sharingan—a feat he shared with his older brother. But Madara's constant use of the ability came at a cost: he started going blind. Rather than watch his brother lose his sight, Izuna made the ultimate sacrifice and gave Madara his own eyes. The transplant allowed Madara to unlock an even stronger form of the Mangekyou that wouldn't deteriorate over time.
Izuna lived roughly 70 years before the events of the series.
Content compiled by AnimeList.moe from publicly available sources.
