Kant and Arendt's contemplation on the theory of "Radical Evil" provides two key dimensions for understanding the nature of evil: the potential for evil and the actuality of evil. Kant's theory of "Radical Evil" establishes the potentiality of human malevolence within the realm of the transcendental, whereas Arendt considers the "Radical Evil"represented by totalitarianism as an unfathomable evil in reality. The emergence of the concept of the" Banality of Evil "signifies Arendt's pivotal shift in thought, probing into the possibility of evil from the vantage point of its actual manifestation. To confront the reality of evil, it is essential to not merely perceive it as an entity opposed to good, lest we fall into the trap of the "demon myth". United in their endeavor to "demystify" evil, both Kant and Arendt propose that the potentiality of evil is rooted in human free will. This perspective is not a derivative of theodicy; instead, it reveals the essence of humans as moral beings and their undeniable moral obligations. While free will denotes an inescapable "Radical Evil" within humanity, it also equips us with the strength and hope to resist evil.