In Avengers: Infinity War, Thanos will finally step out of the shadows and take on the combined forces of Earth's Mightiest Heroes. After various teaser appearances and cameos dating all the way back to 2012's The Avengers, there's a lot of hype for the Mad Titan and he's all set to be the biggest, baddest enemy the heroes of the Marvel universe have ever faced. We're sure that the titular team will ultimately be able to take him down, but they're certainly going to have a tough time doing so.