Final answer:
Husayn ibn Ali died a heroic death and was considered a martyr for Islam Shi'ites. His death deepened the divide between the Sunni and Shia branches of Islam.
Step-by-step explanation:
The person who died a heroic death and was considered a martyr for Islam Shi'ites was Husayn ibn Ali. Husayn was the grandson of Muhammad and the son of Ali, the fourth caliph of Islam. He was killed in the Battle of Karbala in 680 AD, along with his family members and companions.
Husayn's death is commemorated by Shia Muslims every year on the day of Ashura, which is a festival of mourning and repentance. The processions held in Karbala, Iraq, where Husayn died, are the most significant events of this commemoration.
The martyrdom of Husayn further deepened the divide between the Sunni and Shia branches of Islam. Shia Muslims believe that Husayn sacrificed his life to defend the true teachings of Islam and to uphold justice against tyranny and oppression.