Forget whatever you think you know about The Avengers' villains. The latest rumor changes everything. Guess who the second villain in Marvel's big picture could be!
Spoilers from here on out...
Latino Review has exclusively revealed that The Avengers big foe (besides the already reported an confirmed adopted brother to Thor, Loki) will be none other than Thanos. They won't say how he's in the film or why, just that he's in there.
And while we're still taking this with a grain of salt, LR could be right. Thanos is directly associated with The Infinity Gauntlet: a glove that gives the wearer (when it has all of the infinity gems intact) infinite power, and we've seen said gauntlet on prominent display at Marvel's San Diego Comic Con booth as well as hidden in Odin's vault in Thor. And we can't imagine why they would keep waving this around if they weren't planning on attempting to bring Thanos into the mainstream.