What is a general definition of “evil” that one could derive this from? And how does this relate to the actual reasons why someone would inflect physical pain?

What is a general definition of “evil” that one could derive this from? And how does this relate to the actual reasons why someone would inflect physical pain? Are soldiers in a war evil when they happen to inflict physical pain outside of self defense? Or is that another “common-sense” exception? The concept is emotionally laden and ill-defined, and has little relation to why the designated behaviors actually happen. It’s an incoherent concept that has no explanatory power.