Answer
The answer is Ali, the fourth caliph of the Rashidun Caliphate. The First Fitna, also known as the First Muslim Civil War, was a conflict between supporters of Ali and those of the Umayyad dynasty, who sought to avenge the assassination of Uthman, the previous caliph. The conflict had far-reaching consequences, dividing the Muslim community and establishing the Umayyad dynasty as the rulers of the caliphate.