Why do people think Cersei is this utterly evil character without redeeming qualities? She's no Ramsay Bolton or Gregor Clegane.
Cersei is easily the most tragic villain in the series. She wasn't a evil girl growing up. She may have been cold and prideful, but that can be blamed entirely on her father. It wasn't until her marriage to Robert where he raped her constantly that she became evil.
In short, I would say Cersei really isn't evil at all. If she were raised by a decent man, and wasn't sold off to an abusive husband, she'd be more like a Catelyn Tully type figure.
As we've seen in AFFC, Cersei is NOT intentionally evil. All of her cruel acts are done to protect her and her children. Yes, she goes off the extreme in some cases, but who wouldn't be?
Tyrion the Valonqar. Jaime the betrayer. Tywin dead. Joffrey dead. Enemies everywhere.
That's my argument.