This article delves into the religious justifications used by extremists in Islam and Christianity, examining key religious texts and socio-political factors influencing violent extremism. By examining historical and modern cases, such as the Crusades, jihadist movements, and Christian extremist groups like the Ku Klux Klan, the article examines the weaponization of religious rhetoric to promote violence, the roles of religious leaders (be it inciting violence or promoting peace), and the stride taken by Islamic and Christian scholars to counter extremist ideologies. Through a comparative analysis, the article draws out the similarities and differences in the theological and political motivations behind extremist killings in both religions. The conclusion emphasizes the importance of a deeper understanding of religious texts and the separation of faith from violence, advocating for increased efforts in religious education and interfaith dialogue as essential to combating extremist ideologies.