This paper reviews the relationship between guilt and prosocial behaviors, and integrates multiple antisocial phenomena with the construct of guiltlessness both at the interpersonal and intergroup level. Interpersonal guilt is basically prosocial and introspective. Collective guilt is the vicarious acceptance of misdeeds of the ingroup. Yet it is sometimes so painful and detrimental for the individual and the society to tolerate guilt that people do not feel guilty, especially when the possibility of reparation is low. We argue that guilt is the acceptance of the mildly undesirable self whereas guiltlessness is the rejection of unbearable mental distress of anticipatory guilt. Guiltlessness requires great efforts for defense and justification. Multiple strategies and justifications are sought to relieve guilt. Furthermore, guiltlessness is related to various personality and ideology variables and entails moral disengagement. Guiltlessness can be destructive because, for example, during times of large-scale conflicts ordinary people who feel guiltless are inclined to become ruthless. Reciprocity morality, ostracism, deservingness, empathy, and self-control are proposed as means of explaining the origins of guilt and their implications for guiltlessness.