2. Theon's Castration and Torture
HBOBasically Theon's entire fourth season arc. Out of all the characters on the show, Theon is the one who pays the most for his trangressions, despite arguably not even constituting as a villain. You might have been wanting Theon to get his just desserts after being such an insufferable prat, but even he doesn't deserve the fate that befalls him. After a disastrous siege on Winterfell that he and his people were unable to maintain, he became a prisoner of Ramsey Snow, a sociopathic bastard who inherited his father's penchant for flaying. Ramsey toys with Theon for months on end, destroying him both mentally and physically, until there's nothing left but a sad little man named Reek. But the worst part of the whole ordeal was Ramsey's sick game with Theon prior to his castration. He brings two girls into his cell to throw themselves at Theon, to give him one last bit of hope before brutally ripping it away. The show shows uncharacteristic restraint in that we don't see Ramsey actually castrate Theon, but we know exactly what happens, and it's one of the most uncomfortable and genuinely nauseating moments on the show.