The MCU is known for being a family-friendly experience almost all the time. There is plenty for adults and children alike in the Marvel Cinematic Universe. However, there is a consensus among the filmmakers of the MCU that the focus should usually be on building a universe by introducing more characters.
Continuing to build a universe, as it expands almost beyond the size where most fans can keep track of everything, means not killing off many characters. Still, several have had a permanent death (as far as audiences know) and others have created their own heart-breaking moments of sadness that have been made part of the infamous history of this universe.
8 I Don’t Feel So Good (Avengers: Endgame)
This was the first of many emotional moments to come from the Infinity War/Endgame duo of movies that wrapped up so much in the MCU. The Snap was a devastating moment that killed off many heroes and broke the entire universe of the MCU, for five years at least. But the emotional crux of this moment came on Titan. Thanos’ former home world's population was more than halved by this blow, as only Tony and Nebula made it out.
The other Guardians, Doctor Strange, and Peter Parker were all lost to the Snap. Parker’s loss was felt most keenly, as his final emotional moments with Tony Stark have become infamous, and was hugely important in spurring Tony to pretty much invent time travel.
7 Let Me Go (Avengers: Endgame)
Another moment from the devastating duo of films was the great sacrifice that had to be made to retrieve the Soul Stone in Avengers: Endgame. Natasha and Clint, Black Widow, and Hawkeye, always best friends, had to choose which of them would be sacrificed for the stone.
Battling each other one final time, as they have done on several occasions, for the privilege of death, Natasha wins out. Her final plea to him to let her go was one of the most devastating moments the franchise has ever seen. It was a particularly keen loss since she was finally due to get her own movie the following year, finally helping her MCU counterpart be as good as Marvel Comics Black Widow.
6 With Great Power (Spider-Man: No Way Home)
The MCU’s phase 4 may have been a mixed bag as far as many fans and critics are concerned. But the most universally-beloved project of the phase is perhaps Spider-Man: No Way Home. The hype surrounding this film individually was at a fever pitch rarely seen, even in the MCU, and it didn’t let fans or critics down.
The emotional crux of this film was the loss of Aunt May. After meeting his other selves, who had already witnessed their guardians die, Peter 1 had to deal with the loss of his Aunt May. In her final moments, she delivered this famous line about power and responsibility which made the death even more devastating and reminiscent of past Spider-Man franchises, which Spider-Man is returning to in phase 5 as a street-level hero.
5 So Long Darling (WandaVision)
WandaVision was the first MCU project to hit Disney Plus first. This TV show baffled viewers by jumping between various themes for the first few weeks. It came down to a battle between Wanda and Agatha, and Wanda had to admit that she couldn’t, or shouldn’t, keep up the barrier around the town forever.
Before ending the barrier once and for all, Wanda and her recreation of Vision have a final moment alone. This ending was heart-breaking, even more so in retrospect. Wanda’s current status is unknown, but the dark path this loss sent her down is truly hard to witness in Multiverse of Madness as she becomes the dangerous Scarlet Witch.
4 I Can Do This All Day (Captain America: Civil War)
Captain America: Civil War is another powerful, emotionally-charged MCU movie. Despite none of the heroes in the movie actually dying (unless King T’Chaka is counted) there is a keen sense of loss in the movie as the Avengers are dismantled by the Sokovia Accords.
Tony and Steve eventually come to blows culminates in the finale, where Tony tries to keep Steve down but finds it as impossible to do as everyone ever has. Steve insists he can keep going, as he has against various villains in the past. It was heart-breaking, as this difference appeared to be irreconcilable at that moment.
3 It’s Beautiful (Black Panther)
Black Panther remains one of the most universally-loved MCU movies. The battle between T’Challa and his cousin, Eric Killmonger, was undeniably great. Black Panther was also a hugely emotional journey, and it culminated in a quiet moment as Killmonger’s life came to an end.
After being defeated and fatally wounded by T’Challa, Killmonger made the choice to simply sit and watch the sunrise. His reflective ending and the moment of peace he achieved made this death and moment far sadder than audiences were expecting.
2 What Did You Do? (What If...?)
This list would be incomplete without mentioning What If. The animated Disney Plus series is a widely varying collection of emotionally-mixed stories. This wildly-changing style made sense for what the show was trying to achieve. But fans cannot forget episode four of the first season.
This episode, entitled “What If… Doctor Strange Lost His Heart Instead Of His Hands,” features Strange trying to save his love, Christine Palmer, but failing at every turn. Eventually, he completely breaks time and destroys his own universe trying to keep her. This culminates in Stephen being left alone at the end of the universe as she vanishes, asking him "What did you do?" in her final moments.
1 I Am Iron Man (Avengers: Endgame)
Perhaps the most heartbreaking moment in the MCU, and the moment when the Infinity Saga truly ended and new beginnings occurred, was this moment. The words, spoken after Tony stole the Infinity Stones from Thanos during the incredible final battle, and attached them to his suit, were his last in life.
The audience, having seen Tony Stark go from a selfish billionaire to the man willing to make this sacrifice, could not have been more emotionally devastated by this loss. The complete journey of the MCU up to this point had been about Tony’s journey and emotional maturation. Finally, beating Thanos at this great cost, was a triumphant moment, but Tony’s death was heart-breaking in the extreme.