Izuna Uchiha

was the younger brother of Madara Uchiha, who was known as the strongest Uchiha. He bears a striking resemblance to Sasuke Uchiha.

Background
Eighty years prior to the start of the series, Izuna and his older brother were said to be equals as the most gifted members of the Uchiha clan, and they usually compete with each other everyday, getting stronger. Both awakened their Sharingan early in life, and they became the first Uchiha to awaken the Mangekyo Sharingan. Madara used the power of his Mangekyo Sharingan to take control of the clan with Izuna at his side. When Madara eventually went blind, he took Izuna's eyes to regain his sight. Itachi Uchiha suggests his eyes were taken by force, but Madara insists Izuna willingly gave up his eyes for the good of his brother and the clan. According to the third databook, Izuna later died in battle.

Abilities
As the younger brother of Madara Uchiha, the strongest of the clan, Izuna himself was said to have been equal to his brother in every way. Both of them have exceptionally high levels of chakra, even for Uchiha members.

Izuna's Mangekyo Sharingan, developed some time after Madara, took the appearance of three bars stretching out of his pupil. When Madara took his eyes, the two's Mangekyo combined. Izuna's loss of his eyes rendered him blind, but he managed to survive and continued to battle. However, with this sudden disability, it led to his eventual death on the battlefield.

Trivia

 * is the name of a wind spirit, and can be translated as "rice-rope".
 * Izuna shares a birthday with fellow Uchiha, Obito Uchiha.