When a character dies in the comics, it's a bit of an inconvenience, seeing as they pretty much always come back sooner or later. In the MCU, it's a bit different; when a character kicks the bucket on the silver screen - unless it's Loki - they're pretty much gone for good. "Coming back" is limited to flashbacks and movies that cover storylines from the past. Maybe an alternate reality via WandaVision or some Infinity Stone shenanigans might help, but otherwise, a dead MCU character remains deceased.
Because of this, the scenes featuring those demises are often monumental affairs, and there are some fascinating tales behind how they came about. The way they were filmed, the things that were spoken, and the manner in which the characters perished tend to leave a mark. This list highlights the most interesting stories behind some of the most memorable MCU characters' death scenes.
Tony Stark's demise was one of the most heartbreaking of any superhero movie to date, and there's a good reason for it. If you go back and rewatch the scene, you will notice that after his famous retort to Thanos, "I am Iron Man," he doesn't say anything at all. This was a choice that was made in contrast to the script, and much of the scene was improvised.
It was Robert Downey Jr. who insisted Stark remain quiet as he lay dying on the battlefield. The screenwriters wrote "lovely dying words for Tony Stark," but Downey had another thought. Stephen McFeely said that "a guy who has talked and talked and talked for many, many movies - when he doesn't talk, you are crushed." He was right, as was Downey, because that scene hit everyone who watched it hard.
Concerning Iron Man's final words, the Russos worked hard to figure out what he should say because saying nothing wasn't working. "We were in the editing room going, 'He has to say something. This is a character who has lived and died by quips.' And we just couldn't. We tried a million different last lines. And our editor Jeff Ford, who's been with us through all four movies and is an amazing storyteller, said, 'Why don’t we just go full circle with it and say, "I am Iron Man?"' And we're like, 'Get the cameras! We have to shoot this tomorrow.'"
Just because they had the line, that didn't mean they could get it filmed because Downey wasn't interested in stepping back into that emotional scene. The movie had already wrapped, and he had to be convinced to do the reshoot to say the line that was a callback to his final words in 2008's Iron Man. Joe Russo explained the story behind Downey's preference to keep the line out in an interview with CinemaBlend:
It's an interesting story. I had dinner with [Robert Downey Jr.] like two weeks before we were supposed to shoot it. And he was like, "I don't know. I don't really want to go back and get into that emotional state. It'll take... it's hard." And crazily enough, Joel Silver, the producer, was at the dinner. He's an old buddy of Robert's. And Joel jumps in, and he's like, "Robert, what are you talking about? That's the greatest line I've ever heard! You gotta say this line! You have to do this!" So thank God that Joel Silver was at dinner because he helped us talk Robert into doing that line.
Thanos was the big bad of the MCU's first few phases, and when he finally made his full appearance in Avengers: Infinity War, he came out swinging in a big way. After defeating the Hulk, he had a conversation with Thor, which would eventually come back around in Avengers: Endgame:
I know what it's like to lose. To feel so desperately that you're right... yet to fail, nonetheless. It's frightening. Turns the legs to jelly. I ask you, to what end? Dread it. Run from it. Destiny arrives all the same. And now, it's here. Or should I say... I am.
That movie concluded with Thanos's infamous snap, and when he returned in Endgame, he was slain early in the first act when Thor heeded his advice to go for his head. Of course, that wasn't the demise of Thanos anyone really talked about - though it did come as a result of his letting them terminate him, as he'd accomplished what he set out to do.
He perished at the end of Endgame in a far more permanent manner, and that end hearkened back to the speech from the beginning of Infinity War. As soon as Thanos realized he had lost, his legs turned to jelly. He sat down and let the inevitability of his destiny come and spread his ashes into the wind. Thanos saw himself as a martyr, and the fulfillment of his destiny was always in the cards.
Of all the characters in the MCU who have perished on screen, Loki has kicked the bucket more than most. He's dying left and right, but it's usually a ruse. Of course, his demise in Avengers: Infinity War was the real deal (until the time-travel shenanigans in Endgame), and the sequence happened pretty soon after the movie began, which left many watching it stunned. Tom Hiddleston described how emotional the scene was and what it meant for the character at an appearance at ACE Comic-Con:
When I came to shoot the scene in Infinity War, I think it's very powerful he calls himself an Odinson, and that closes the whole journey of Loki and what he can do. It [Loki's demise] set the stakes up emotionally. It takes the stakes up dramatically. You know that Thanos is someone who's more dangerous than anyone we've seen before.
Josh Brolin didn't even like filming the scene, which involved choking the life out of the character: "He had been with that character for so long. And he's so lauded for doing it. Tom was so vulnerable at that moment. So, choking him out wasn't the most fun thing I have ever done." It was quick, and it really did feel as if Thanos quickly snuffed out a flame, but it was necessary to convey the force of nature Thanos was in the MCU.
Of course, while it meant a great deal to the story, Loki managed to swipe the Tesseract and escape into an alternate reality in Avengers: Endgame. His story will continue in his eponymous Disney+ series, but that version of Loki isn't the same one who perished. The deceased Loki had a great deal of character development, while the saved version from Endgame has only just terrorized New York City, so Hiddleston will likely have a lot more fun playing the character despite bringing him full circle in Infinity War.
Black Widow's demise in Avengers: Endgame was an emotional one that showed how much she cared about her friends. Granted, Clint was just as devoted, and both characters fought one another so they could sacrifice themselves for each other. That's not only a person who cares about their friends; it's the very definition of a superhero. Her demise was one that couldn't be undone, so it's permanent despite the ever-pending release of her eponymous solo film.
Prior to her end, Clint's story arc was gearing up toward a sacrifice of his own. Natasha had taken over the leadership role of the remaining Avengers while Clint adopted his Ronin persona and was traveling the world to eliminate every bad guy he could get his hands on. He lost everything and was ready to let it all go, but Natasha knew he could get it back, and that's why she valued Clint's life over her own. Her sacrifice was noble, and it was noteworthy, but it wasn't the original plan.
There was an alternate scene filmed that actually minimized the sacrifice. In the deleted scene, Thanos and his forces arrive on Vormir, which forces Clint and Natasha into action. It's not a poorly filmed scene, and the action is intense, but it takes away from the central concept of what it takes to get your hands on the Soul Stone: sacrifice.