Evil acts are intentional assaults upon innocents: the evildoer knows what he is doing and wants to do it to someone who does not deserve it. Essentially, it is a purposeful delivery of unjust suffering. But does the evildoer think his victim to be innocent? What if the evildoer sees his terrible deed as necessary and his target as really deserving? The victims of the Holocaust, in many NAZI minds, were deserving of their fate: eliminating the world of Jews, Bolsheviks, Homosexuals, Cripples, and other Degenerates was an act of Justice...precisely the Just deed, and their terrifying acts were protecting everything beautiful and noble about the world. The Jews were evil and the final solution was how to eliminate the world of their evil influence.Zimbardo: "Evil consists in intentionally behaving in ways that harm, abuse, demean, dehumanise, or destroy innocent others - or using one's authority and systemic power to encourage or permit others to do so on your behalf, In short, it is "knowing better but doing worse."
I don't know if evil can be easily translated apart from the religious context from which it developed. In a purely psychological context it seems to capture an event which cannot be tolerated: deeds which are never appropriate and never justified. But the religious term evil refers to something that offends not simply human values, but is an offense to the very source and foundation of all creation: it is something by which God divides who is welcome in the heavenly kingdom and who is kept out. Still, it really is a complex of the term in Judaeo-Christian theology and biblical studies.