There's a popular fan theory that the real villian of Game of Thrones is Daenerys Targaryen, the mother of Dragons.
Megan Willet of Tech Insider posted a nice explication here.
The whole argument is great, but one photo she posted did the trick on me.
It's this one.
It shows the difference between good and evil
On the left, you have Jon Snow, watching the 6 guys who stabbed him to death hang. He doesn't look happy. For him, killing is a burden — even if it's just.
On the right you have Daenerys, watching a group Khals burn to death. She looks happy. She looks…evil. For her, killing is a pleasure.