The question would be hard to answer , based on the centuries that have come and gone,
But there could be no other then the one who has been living sense Adam and Eve,
The one who has killed countless of humans in the name of war , even under the name of religion.
Notice he is called a murderer.
Joh 8:44 You are from your father the Devil, and you wish to do the desires of your father. That one was a murderer when he began, and he did not stand fast in the truth, because truth is not in him. When he speaks the lie, he speaks according to his own disposition, because he is a liar and the father of the lie.
Anyone who keeps taking life throughout Generations would be evil in that he has killed more humans then one man , group , or army. SATAN is what evil is.