While the Harry Potter series features quite a few antagonists, none are as infamous as Dolores Umbridge. Appearing for the first time in the fifth book, Harry Potter and the Order of the Phoenix, Umbridge is a character who presents a lot of major obstacles for the main characters of the story. She's perhaps the most hated villain in Harry Potter by the fandom, even more so than Voldemort. Even though she's just a normal human with a terrible agenda, that humanity is perhaps what makes her scary, knowing that she's as capable of evil as some of the more malevolent beings in the series.