But, how to define true evil? You may say X is, I may say yes, and so is Y. But Homer over there says neither.
That's why these days we never ever leave the imposition of the death penalty to one individual. It takes 12 people on a jury to recommend death and then the record is carefully scrutinized by others to make sure that everything was properly dotted and crossed. Only then is the person put to death.
Guess what? I would not have executed Timothy McVeigh. I would have put him in a cell surrounded by pictures of all those he killed. Then, on their birthdays, he would be required to write a letter to the next of kin explaining himself. It would be torture. Some would call it cruel and inhuman. I call it penance.
One day, hopefully, he would have broken down and cried the tears of Peter and begged God for forgiveness. Then you could rebuild the man into someone productive.