In the past I did things I now consider evil. Things which violate my values, principles, and ethics-- or at least the ones I have now. Some of those things I even considered evil when I did them, yet I did them anyway. What's up with that?
I feel a lot of guilt for some of those things, but am learning to move on. And I will make up for them.
I realize I am not the same person that I was back then. In very real ways. Pretty much all my cells are different now. Just about every atom in my living systems has been replaced over the years. And my mind, my self, is vastly different-- I have different, more consistent, and more coherent (better) values, principles, and ethics.
I'm far from perfect, but it is now rare for me to do anything I consider evil. Stupid, yes. But not usually evil. I consider that an improvement.
But I know that if pushed, I still have that dark side. Sometimes I feel it. The trick is to control and channel it, and to not let it come out at the wrong time. To never let it archate. To only let it out in times when defensive violence is necessary. And then, to let it be a focused beam, surgically applied to the problem. "Collateral damage" is not an option.