The Marvel Cinematic Universe has built up a truly massive cast of characters, ranging from costumed superheroes and support characters to mighty villains and even cameo characters. To keep the MCU streamlined and focused, writers will write out or even kill off some heroes and villains, though the timing doesn't always feel right.
In many cases, an MCU hero is killed off or written out for emotional impact. In the long run, though, the MCU could have and probably should have kept some of these heroes alive a little longer so they could fight one more time, get a much-deserved break, or interact with new characters like Shang-Chi and Kang the Conqueror. Some characters were also written out for real-world reasons that couldn't be helped, but it still hurts.
10 Black Widow
Natasha Romanoff/Black Widow was in the MCU starting in 2010's Iron Man 2, though she only played a supporting role in most films, including in 2018's The Avengers: Infinity War. Black Widow met her end in Endgame when she gave her life to help Hawkeye secure the Soul Stone.
Black Widow died before she could develop as a character, and though Marvel did release a prequel Black Widow movie, it felt like too little, too late. If the MCU hadn't killed her off, Black Widow could have become one of the MCU's best Avengers in its current phase. It always felt like they treated her as an afterthought and her premature death didn't help.
9 Phil Coulson
Phil Coulson only appeared in the MCU's first phase, and he died at Loki's hands in 2012's The Avengers. While he was a principal character in Agents of S.H.I.E.L.D., it still felt like a shame and a waste when they kicked him out of the main MCU so soon.
As a calm, polite, and professional S.H.I.E.L.D. agent who was never intimidated or fazed, Phil Coulson helped keep the MCU grounded by standing up to Tony Stark's grandiosity and Loki's bombast. The MCU should have kept him around for Phase 2. If he needed to die, he could have met his demise making a difference in Sokovia, not as a speed bump in Loki's escape.
8 Black Panther
After Chadwick Boseman's tragic death in 2020, T'Challa was written out of the MCU. As a result, the 2022 movie Black Panther: Wakanda Forever had its plot changed so Shuri, rather than T'Challa, became the film's Black Panther and the franchise's new protagonist.
Fortunately, Boseman's Black Panther still made his mark on the MCU in his wonderful 2018 standalone movie, and in Civil War and Infinity War. Fans dearly miss the character and actor, though that shouldn't diminish Shuri's newfound prominence as a superhero in Phase 4 and beyond.
7 Queen Ramonda
Queen Ramonda was killed off in 2022's Black Panther: Wakanda Forever, just as she established herself as a prominent leader in the MCU. She was an important and stately presence in Black Panther but didn't truly get her chance to shine. The MCU will miss her untapped potential almost as much as her son's.
Queen Ramonda was a remarkable character. A politically savvy, sympathetic, and strong-willed leader and mother who set a fine example for all Wakandans, Ramonda was a fan favorite for a reason. In the narrative, she died to make Shuri's emotional arc more resonant, and hopefully, Shuri will see her again in the Ancestral Plane.
6 Loki
Even if the villain turned antihero Loki lives on in his own Disney+ TV show, MCU fans still miss Loki's role in the main MCU. He was a total villain in Phase 1, but during Phases 2 and 3, he became a more sympathetic antihero and a true brother to Thor Odinson.
Loki had finally become a real MCU hero, just in time for the mighty Thanos to strangle him to death in Infinity War's opening sequence. Thor and MCU fans everywhere were hit hard by Loki's gruesome demise, which set the tone for the grim, omnicidal movie.
5 The Ancient One
Doctor Strange made his debut in the MCU's Phase 3 and he learned much from the Ancient One. To create a sense of passing on the torch, the movie killed off the Ancient One and made sure that Doctor Strange was Earth's new #1 sorcerer, but it felt like such a waste.
If she had lived, the Ancient One could have helped mentor Doctor Strange and fight back against Thanos as well. Even in Phase 4, with Doctor Strange battling the mighty Scarlet Witch, the Ancient One could have done a lot of good and helped prevent the upcoming multiversal catastrophe. With Kang now in the MCU, and Incursions obviously pending, it would have meant a lot more if she'd died saving the universe and preserving reality's integrity.
4 Captain America
On the plus side, Captain America's farewell was a touching and satisfying way to end his character arc and Phase 3 alike, but fans still weren't ready to bid Steve Rogers farewell. Cap was a founding Avenger, and his charismatic leadership was the glue holding the team together.
Captain America's standalone movies rank among the MCU's best, with The Winter Soldier and Civil War leading the pack, and he was also a major player in Endgame. MCU fans trust Sam Wilson to carry on Captain America's name going forward, but even so, the MCU doesn't feel the same without that skinny kid from Brooklyn.
3 Vision
The robotic Avenger Ultron made his debut late in Phase 2, in 2015's The Avengers: Age of Ultron. Vision sternly rejected Ultron's ideology of machine supremacy and fought bravely alongside the Avengers afterward. However, Thanos tore the Mind Stone out of his forehead and killed him.
Many fallen Avengers returned in Endgame, but Vision wasn't among them. He died before the Snap and can't exist without his Mind Stone. Vision appeared in WandaVision, and the White Vision variant is out there somewhere but MCU fans really wanted to see him return to the MCU's principal continuity.
2 Yondu Udonta
Yondu Udonta was more like a supporting villain in 2014's Guardians of the Galaxy, but the sequel redeemed the character in Phase 3, finally establishing Yondu as the foster father Peter Quill needed. Yondu's sacrifice in Volume 2 felt very meaningful but it came with a heavy price.
Guardians fans would love to see Yondu return in Volume 3 just so he could support the Star-Lord and prove himself as the galaxy's deadliest whistler, but it's too late for that now. Yondu died and he was given a Ravagers funeral. It's fun to imagine where Yondu's heroic arc might have taken him but at this point fans can only speculate.
1 Heimdall
Heimdall was one of many casualties in Infinity War, dying moments before Loki in Thanos's attack on the Statesman in deep space. Heimdall once guarded the Bifrost and was a loyal friend to Thor and Odin, but he went on the run when Hela rose to power and fled with the rest of the Asgardians when Surtur destroyed Asgard entirely.
Heimdall lost a lot, then lost his life to Thanos. Fans never got to see many facets of Heimdall's personality, and seeing his personal life in New Asgard on Earth could have been hilarious and dramatic in turns. He did appear briefly in Thor: Love and Thunder in the afterlife, escorting the recently deceased Jane Foster to the waiting Valhalla, but the Thunder God will miss his all-seeing eyes and stoic wisdom.