When I was a child, I believed that villains were people who knew they were bad, and hated goodness. That was what cartoon supervillains were like: their organizations had names like “League of Evil”, and they wanted to do things like stamp out all color and happiness in the world.
Later, I realized that the villains I knew from childhood were unrealistic. Black-and-white caricatures for people without complex moral understanding. No one thinks of themselves as evil, and certainly no one would describe themselves as such, declare themselves the enemy of things good and right.
Now, I’m a little older yet, and I realize that I was only half right. It’s true that there are very few people who think of themselves as evil (and most of those that do need a hug and a therapist more than they need to be stopped for the good of the world), but there are definitely people who will declare themselves the enemies of virtues. People who make empathy a punchline (and never mind that it’s literally the only thing that keeps a person from sociopathy), people who really do scorn compassion as weakness (or even a sin, if applied to the “wrong” people).
It’s disturbing. People who talk and act just like cartoon bad guys straight out of my childhood, but who have themselves convinced that they’re the good guys.
That’s what makes them scary. If they’re already the good guys, they can never reform.