Who Kills Thanos? - Predicting Avengers: Infinity War's Climax

3. Thor

Ordinarily, the fact that Thor is one of the original Avengers and has his own trilogy completed might put him in the Dead Meat category, but the God Of Thunder is an important part of the Infinity War narrative in a very telling way.

As revealed by the story details we know already, Thor heads off on his own mission at one point (along with Rocket and Groot) to retrieve a weapon to replace Mjolnir. The fact that Ragnarok firmly established that he's capable of harnessing his powers without a weapon at all suggests that he's looking for Stormbreaker for another reason.

The logical progression would be that Thor needs Stormbreaker to help bring down Thanos (perhaps not in direct conflict) and that the weapon is the decider in the ultimate battle. It's definitely a more out-there theory, but there has to be some reason for him needing a new weapon.