This site examines Macbeth and the nature of evil. It actually says that evil is the opposite of humanity. It is a deviation from what is natural. (I can see problems with that definition.) But then the author goes on to say that evil originates in the human heart. It’s a start. Finally.
An article on what Hamlet meant to some African tribesmen. (Didn’t say what tribe.) They explained the plaly to the American telling the story. It was much different.