I don't like the word evil. It has supernatural connotations, and there is no supernatural. All animals are subject to brain defects, so all animals can potentially act inappropriately.
Evil is not supernatural. But i partially agree with you.
For example, Hitler was evil. Although he was also pumped full daily with all kinds of experimental drugs. Easier to make dreadful decisions when you are under influence. Also handy for soldiers. As can be seen in the past by the use of amphetamines. And criminals behaving violently and being paranoid because of the cocaine or meth or bath salts. So, there is the brain defect.
The question comes down to : In to what extent do you have to remove someones personality and character traits before they would choose to harm others and even might enjoy it ?
Everybody is capable of doing evil. It just depends on the person how much barriers they have naturally and how much they have created consciously to prevent them from doing unspeakable things.
The whole angel and devil story that resides in everyone.
Religions are not just wacky ideas. Sometimes it does contain some psychology based on experience. It is just that religious texts are mostly to be learned from and understood what is meant, not to be interpreted literally by the word. Biggest flaw of the human world.