Worst: The Mariah Carey-Nicki Minaj Feud, Season 12
After original judges Paula Abdul and Simon Cowell left in Seasons 9 and 10, respectively, American Idol had a hard time filling their shoes. It went for music industry cred with songwriter Kara DioGuardi, then high-profile fish out of water Ellen DeGeneres, to beloved but befuddled rocker Steven Tyler before hitting rock bottom in Season 12 with dueling divas Mariah Carey and Nicki Minaj, who seemingly hated each other. There was teeth-sucking, eye-rolling, harsh words, cold shoulders and even an implied threat or two. While some questioned whether it was real, Carey has since said the experience was like "going to work every day in hell with Satan."