Anthony Russo: The ending of that movie, it's a difficult ending, the ending of Infinity War, and it's really important for us to double down on that and commit to that, and figure out how does someone move forward from a moment like that? How do these heroes move forward from a moment like that? That's the story that we want to know.

Joe Russo: They lost.

Anthony Russo: Exactly. And that's a real experience. So we wanted to give that its due.

Joe Russo: It was a unique opportunity for us in Infinity War, which is an exceedingly expensive movie, and we had a studio very supportive of us killing half the characters at the end of the movie. That as filmmakers is a really rare opportunity, and we wanted to take advantage of that opportunity.