Maybe the 'evil' is suppressed pain and anger? Working with a therapist on constructive ways of releasing it might be more beneficial.

Sorry but I don't go with the devil business. All of us have anger and pain inside us, most people occasionally worry they;re going crazy or will even kill someone or whatever. It's normal to have such thoughts and emotions. Acting upon them is a whole different story.

Try to understand yourself rather than making yourself evil and i would suggest some support to uncover what's going on inside.