Person
Abd al-Rahman ibn Muljam
عبد الرحمن بن ملجم
d. 661 CE
Kharijite who assassinated Ali in 661 CE during prayer in Kufa.
Significance
Assassin of Ali, marking a turning point in the First Fitna
Reputation in tradition
condemned
Stated motivation
Opposition to Ali and his arbitration with Mu'awiya
Sources: Wikipedia and classical Islamic biographical literature compiled by automated researchers. Every page is being continuously refined — if something looks off, please check back in a few days.