There is such a thing as a sociopath -- a person commonly described as without a conscience -- and I suppose if you put that in the same person with a strong sexual sadism perversion, one would have a product we would easily call evil.

This however doesn't address the point I was making which is more philosophical and not psychiatric.  To call a person evil is a judgment and I think it is not only morally wrong but also unscientific and simply a  mistake to make judgment calls about people, good or bad.  The individual described in my first paragraph is extremely unlucky  to have such an inheritance or development, and needs help and deterrence, but thinking of them as evil distorts the reality.  They act out of internal desires and instincts, not much different from a cat playing with a mouse it has caught rather than dispatching it immediately.

In short I think evil is a word generally best avoided or just used as a form of shorthand to indicate strong personal disapproval but not as a description of something real in the world.