Inside the halls of Hogwarts School of Witchcraft and Wizardry, Harry Potter (Daniel Radcliffe) and his pals have seen their share of bad teachers, including Defense Against the Dark Arts teachers as Quirinus Quirell (Ian Hart), Gilderoy Lockhart (Kenneth Branagh) and Dolores Umbridge (Imelda Staunton). But arguably the worst teacher is Severus Snape (Alan Rickman), who has seemingly worked extra hard to make Harry's life miserable at Hogwarts from the very beginning and **spoiler alert** ultimately reveals himself to be an ally to Harry's arch-nemesis, Lord Voldemort (Ralph Fiennes).