1. Otto Hightower
Compared to villains from Game of Thrones, Otto Hightower isn’t really all that bad. He’s no Joffrey Lannister or Ramsay Bolton. But in House of the Dragon, he’s the worst of the worst. From the very beginning of the series, we learn that he’s desperate for power. He’s the Hand of the King to Viserys, and he wastes no time trying to make his daughter the queen once Viserys’ wife dies. He has absolutely no shame and will do everything he can to climb the social ladder.
Though they’re close by the end of season 1, Otto treats Alicent very badly. He forces her to marry Viserys in hopes that his future grandson will be the next king, and he makes sure she knows her place in the world. Of course, he’s playing the game and making her aware of her reality, but by doing this he also cements it. He might think he’s doing the right thing, but it just comes off as selfish.
Because of his power-hungry ways and the side he’s fighting on, I absolutely cannot stand Otto Hightower.