Remember that Red Wedding? It was all Walder Frey's doing. Sure, Tywin Lannister had a hand in it all, but Frey provided the venue and swords that brought the Stark house down. He had Talisa stabbed her pregnant stomach and then laughed as Robb held her for the last time. Plus his view of women as disposable makes us think violent thoughts. We really couldn't hate anyone anymore than we hate Walder Frey.