In the Victorian era the nature of evil was described in the story of "Dr. Jekyll and Mr. Hyde. An otherwise kind and useful member of society was changed into a drooling psychopathic monster by ingesting a chemical composition. The duality of mankind. And, of course, the ingested chemicals are allegorical.
As they say, that was then, this is now. What is the core of modern evil. You might claim it is drugs or money, or perhaps permissive religious tenets that empower those that have no power. There may even be others. But at the core it is the devaluation of humanity. Not just the devaluation of the victim, as important as this is. Even more important is the devaluation of the humanity of those that do evil unto others. Their hate degrades them into less than animals
Wives that get beaten, those poor little girls in Nigeria, people that will allow themselves to be humiliated for another's pleasure, yes, even those that ply their trade as "escorts" are victims of evil because they either cede control or control is taken from them. Some have recourse, some have none. A judge in the Sudan sentenced a married, pregnant woman to having her child, nursing the baby, And then to be hanged for apostasy. She married a Christian man. Needless to say, the judge is Muslim.
Without logic those in the middle east of the Muslim faith hate all things western and they fear change. Most of all, they hate that which is different. Their sharia law reflects this. The existential question is, does the hate create the fear, or does the fear create the hate? Perhaps, neither. I would not want to think that hate is the nature of man. Therefore, accepting that, there must be an additional impetus that causes one to hate.
Accepting that, that which impels one to hate and directs the focus of that hate is intrinsically evil. So one that is consumed by hate must ask why and how this behavior was learned and nurtured. Those filled with this overriding hate say they are following the directive of their holy book, the Quran, in their thoughts and actions.
So Allah and their holy book directs them to hate and kill? But hate and the killing of innocents is, by it's nature, evil. I believe this is the definition of a conundrum. Unfortunately, evil actions will likely beget evil reactions at some point. And the flame will be lit.