Whereas research focusing on stable dispositions has long attributed ethically and socially aversive behavior to an array of aversive (or “dark”) traits, other approaches from social–cognitive psychology and behavioral economics have emphasized the crucial role of social norms and situational justifications that allow individuals to uphold a positive self-image despite their harmful actions. We bridge these research traditions by focusing on the common core of aversive traits (the dark factor of personality [D]) and its defining aspect of involving diverse beliefs that serve to construct justifications. In particular, we theoretically specify the processes by which D is expressed in aversive behavior—namely, through diverse beliefs and the justifications they serve. In six studies (total N >25,000) we demonstrate (a) that D involves higher subjective justifiability of those aversive behaviors that individuals high in D are more likely to engage in, (b) that D uniquely relates to diverse descriptive and injunctive beliefs—related to distrust (e.g., cynicism), hierarchy (e.g., authoritarianism), and relativism (e.g., normlessness)— that serve to justify aversive behavior, and (c) a theoretically derived pattern of moderations and mediations supporting the view that D accounts for aversive behavior because it fosters subjective justifiability thereof—at least in part owing to certain beliefs and the justifications they afford. More generally, our findings highlight the role of (social) cognitions within the conceptual definitions of personality traits and processes through which they are expressed in behavior.