The Marvel Cinematic Universe has been careful not to permanently kill off many heroes in the first ten years of its run. We've seen fake-outs, resurrections and near misses, but with the exception of Quicksilver, core heroes have fared pretty well so far.
However, it seems like this has all been building up to a lot of death in Avengers: Infinity War. This became especially clear in the latest trailer, which is essentially just a montage of different Avengers getting tortured and beaten half to death.
There are some heroes who look to be in particularly dire situations, like the Vision. Since the Vision’s connection to the mind stone could very well be the thing that keeps him alive, he probably isn’t headed towards a happy ending. While Paul Bettany has hinted that the Vision might not need the gem to survive, having it forcibly removed from his face is certainly going to cause some negative effects.
We also see Thanos holding Thor’s head in a way that looks like he could squash it like a melon. Since this seems like it will be relatively early on in the movie based on how Thanos’ ship runs into Thor at the end of Ragnarok, this probably won’t be the way the King of Asgard goes out. However, many have speculated that this will be where Loki ends up biting the dust.
Doctor Strange is then seen being tortured by Ebony Maw, a scene that has prompted lots of speculation. The trailer then closes out with both Captain America and Iron in desperate situations, with Thanos seemingly about to kill each of them.
The Russo brothers have said that the characters who die in the movie are going to stay dead, and if one of those characters happens to be a founding member of the Avengers, the MCU is soon going to look very different.
While there are going to be a ton of heroes in this movie, the loss of some side characters would not have the same emotional effect as the loss of a character that has been a part of the Marvel Cinematic Universe for the better part of a decade.
Among the original Avengers, Thor, Captain America, and Iron Man all have their deaths teased the most in this trailer. Of course, this doesn’t mean they’ll necessarily end up getting killed. Captain America: Civil War made many people think War Machine was done for, and some fans, myself included, thought Cap would meet his demise.
The movie might not go down this route, but there’s a decent chance one of the original members aren’t going to survive Infinity War. Hawkeye is noticeably absent in the trailer and all marketing materials, which could mean a whole host of different things. Mark Ruffalo has referred to Bruce Banner and Natasha Romanoff as star-crossed lovers, so it’s possible one of them is going to be killed off.
But do one of these characters have to die to prove that the stakes are high? It all depends on execution. Going back to Civil War, none of the Avengers died in the airport fight, but after War Machine got hit by the Vision's blast, it felt like somebody easily could. While some heroes are going to have to lose their lives in the fight against Thanos, what’s most important is building an atmosphere that makes us think anybody could be a goner.
Even though many fans have been clamoring for some real stakes, if too many familiar faces die, there will surely be complaints that the next lineup of Avengers isn’t as good as the old one. Considering this, and the fact that fans are going to want meaningful deaths and not just bodies dropping left and right, the Russo brothers have a pretty difficult job.
In order to achieve the apocalyptic stakes that the trailers promise, Infinity War will have to not just kill a bunch of characters, but kill the right characters. Since we don’t really know where the story is going to go in Avengers 4, it’s impossible to say who these characters are, but it’s a safe bet that one of the founding members of the team is going to die.
No matter what the consequences of Thanos’ invasion are, they are going to greatly impact where the series goes from here. Since this has been a film ten years in the making without any real precedent, there’s no template for how Marvel should handle character deaths—and that’s part of what makes this movie so intriguing.