Evil actions are defined as repeated or persistent, not commensurate with provocation and causing extreme harm, at times due to repetition. Evil develops or evolves. As individuals and groups harm others, they tend to develop characteristics that make further and more intense harmdoing probable. In this article, I explore instigating conditions (difficult life conditions in a society, group conflict); cultural characteristics; the nature of evolution, with its psychological and social processes in individuals and groups; and the passivity and complicity of bystanders that lead to genocide and other collective violence. I consider the question of whether bystanders can be regarded as evil, focusing on the genocide in Rwanda as an example. I examine the socialization and experience of children and youth that lead to aggression and the subsequent evolution of aggression toward greater violence and evil. I explore the way personal characteristics and a system of relationships can lead to sexual abuse by fathers. One organizing concept in understanding the generation of violence that causes extreme harm is the frustration of basic human needs and their subsequent destructive fulfillment.