In Avengers: Infinity War, Thanos reluctantly killed his daughter Gamora in order to secure the Soul Stone for the Infinity Gauntlet. In a new fan theory posted to Reddit (now unfortunately deleted), user CaptainCayden2077 convincingly argues that the Avengers will be forced to make a similar sacrifice in the upcoming Avengers: Endgame.
Nebula and Tony Stark end that film on Titan, separate from the other surviving Avengers in Wakanda. That means that Stark is the only one in a position to know what Nebula knows: why and how Gamora died.
CaptainCayden2077 thinks that Iron Man and Captain America will end up on the same cliff on Vormir in Endgame and that Red Skull will reveal the nature of the necessary sacrifice to Cap the same way he told Thanos in Infinity War. Realizing that they’re in the same situation as Thanos and Gamora, Cap will turn to Tony and think that he’s been brought there to be sacrificed.
The theory is predicated on the parallels between Thanos and Tony Stark: “the two foresaw a great loss, they proposed an idea to counter the loss, they were deemed mad, ‘the mad Titan’ and mad scientists, and what they foresaw came to pass.”
The theory postulates that those parallels will end on the cliff. Instead of sacrificing Cap, Tony will walk to the edge of the cliff and ask Cap to push him off. There’s a conversation all the way back in The Avengers between the two characters in which Cap says that Tony “would never be the one to make the ‘sacrifice play.'” Upon realizing that Tony’s plan was to sacrifice himself, both Cap and the audience will be overwhelmed, according to CaptainCayden2077’s theory.
The Redditor also supports his theory with comments from the Russo brothers, the directors, that Cap’s story arc is larger in Endgame than Infinity War. And because Tony’s worst fear is losing everyone around him, as in his vision in Age of Ultron, it would be fitting for him to give himself up, preventing that fear from ever coming true.
We’ll find out if this theory is correct when Avengers: Endgame (finally) hits theatres on April 26.