Harry Potter/Avengers AU
The Avengers are a team of Witches and Wizards fighting against the Dark Lord Thanos.
Tony is the mad Wizarding inventor who is a genius with a wand. Bruce is a part-time healer, full-time shape-shifting werewolf. Clint and Natasha are Unspeakables. Thor is a Quidditch beater. And Auror Steve has one hell of a shield charm.
(Oh, and Loki is a Death Eater, which no one is surprised about)