Avengers 4: 10 Theories From The Endgame Trailer

The most striking theory of all comes from not what the trailer shows but rather, what it doesn't: what if Thanos isn't the antagonist of this film?

The trailer only briefly shows Thanos, his armor hung up as he enjoys his self-imposed rest, and then kind of avoids him for the rest of its runtime. On the one hand, this is a concentrated effort to focus on the Avengers' struggle to undo the damage he has already done. But on the other hand, they might wind up facing an even bigger threat in Endgame, one who was briefly teased in Infinity War.

In the Vormir sequence from Infinity War, when Thanos gets the Soul Stone, a portal opens up above him before the film abruptly cuts to black. This portal and the nature of the Soul Stone itself remain unknown variables in the story and it is all but certain that these elements will play crucial parts in Endgame. There's also precedent for this in the comics, as Thanos has to face some of Marvel's even bigger baddies like Galactus in the Infinity Gauntlet storyline.

He even eventually turns into something of an anti-hero after being defeated and Endgame might just see him following the same path, possibly even resulting in him teaming up with the Avengers.