Part of what makes the Marvel Cinematic Universe so much fun is how plotlines can not only expand over multiple movies but get satisfying pay-offs. Just look at the journey of Captain America, which spanned nearly a decade and ended on an emotionally affecting note that brought his story back to the woman he loved. Ditto the saga of Iron Man, which saw a man who once cared only for himself sacrificing himself for all of existence. The way these plotlines can breathe over years and years makes their resolutions all the more gratifying. But that doesn’t mean that every single storyline in the MCU has gotten a proper ending.
In fact, several storylines in this expansive franchise have ended up just fizzling out entirely despite being tailor-made for exciting continuations. Everything from teases of famous supervillains to seemingly critical relationships centered around certain superheroes has gotten shockingly little in the way of concrete resolution. The reasons are varied for why a franchise that prides itself on offering up cathartic resolutions of existing plotlines would abandon these narrative threads. In some cases, it’s due to a certain sequel not getting made while other stories are victims of the MCU’s narrative focus shifting to other priorities. Whatever caused these plotlines to remain unresolved, they now stick out like a sore thumb in the Marvel Cinematic Universe.
The origin of The Leader in The Incredible Hulk
At the end of "The Incredible Hulk," Tim Blake Nelson’s Samuel Sterns is coerced into giving Emil Blonsky (Tim Roth) a medical procedure that turns him into The Abomination. As Blonsky charges out of Sterns’ office, he sends the scientist flying into a wall. As Sterns lies on the ground, a small drop of Hulk’s blood falls from a nearby table onto a wound on Sterns’ forehead. The man’s head begins to bubble and, just like that, the origin story of Marvel Comics villain The Leader is put into motion. The producers of this project were hoping Sterns could return in an "Incredible Hulk" sequel with The Leader’s green skin and enormous cranium.
However, "The Incredible Hulk" didn’t light the box office on fire and there were also rights issues regarding further solo "Hulk" movies, leaving a reappearance by The Leader in limbo. More than a decade after "The Incredible Hulk," other characters from that Marvel Cinematic Universe entry, such as General "Thunderbolt" Ross and even The Abomination, have come back to play a part in newer movies. But the origin story of The Leader has never been followed up on and it doesn’t appear to be something that’ll get expanded upon anytime soon.
Darcy and Ian’s romance in Thor: The Dark World
In "Thor: The Dark World," a comic relief character got her own comic relief sidekick. Darcy Lewis (Kat Dennings), Jane Foster’s humorous intern from the first "Thor" film, got an assistant to help her lug things around in the form of Ian Boothby (Jonathan Howard). The two have a mildly conflict-ridden dynamic throughout the adventure before abruptly kissing during the invasion of London by the Dark Elves. Despite being around for so much of "Thor: The Dark World," Ian didn’t possess much in the way of personality. He was just another Earthbound human who delivered small quips and was ill-equipped to deal with all things superheroic. There wasn’t even much chemistry between him and Dennings, romantic or otherwise. He wasn’t painfully irritating — just not all that memorable.
Ian’s role in the MCU was extremely short-lived. He, like all of Thor’s Earthbound cohorts, did not return for "Thor: Ragnarok." In the years since, however, Jane Foster (Natalie Portman) has managed to land a comeback in "Thor: Love and Thunder" while Darcy returned in "WandaVision" as a full-fledged doctor. Yet Darcy made no mention of Ian despite the two locking lips during the climax of "The Dark World." Their romance, and the character of Ian altogether, was just not meant to last very long in this franchise.
Pepper Potts and Tony Stark taking a break
In the middle of "Captain America: Civil War," Tony Stark drops a bombshell on Steve Rogers: he and Pepper Potts are taking a break. After the character was absent from "Avengers: Age of Ultron" due to her duties to Stark Industries, this confirmed that Stark was officially single again, thanks in part to his non-stop adventures with the Avengers. Stark’s wealth would make it seem like he could have anything at his fingertips but he couldn’t keep the woman he loved around.
It was a significant development that played into the darker headspace that Stark occupied in "Civil War" and explained why he felt the need to embrace the Sokovia Accords so he could protect the loved ones he still had. It also helped explain why Paltrow’s Potts was suddenly M.I.A. from the franchise. But this development was abruptly upended in "Spider-Man: Homecoming," when Pepper Potts not only reappeared but was being intimate with Stark as if nothing had ever happened. There was even a gag about Stark popping the question to Potts in lieu of introducing Spider-Man in his Iron Spider outfit to members of the press. The sudden loss of Potts in Stark’s life never got referenced in the following two "Avengers" movies either, making this a strange unexplained detour in the love life of two principal MCU figures.
Erik Selvig’s psychological problems
In the wake of "The Avengers," "Thor: The Dark World" finds scientist Erik Selvig struggling to maintain a proper psychological state. Having had Loki control his mind for an extended period of time, Selvig is now fit to bouts of strange behavior, like wandering around Stonehenge naked. He’s even been locked up in a psych ward, which Darcy and Ian must break him out of to assist Thor in his quest to defeat the Dark Elves. It’s a story development that doesn’t work on a comedy level (too many gags making fun of mental impairments) but it does provide an interesting way of making sure the events of "The Avengers" don’t just disappear.
The lingering aftereffects of Selvig getting his brain scrambled in "The Avengers" wouldn’t last forever, however. When Thor went to recruit the man’s help in "Age of Ultron," Selvig was seen walking out of a college that he teaches at. Not only had he returned to his regular day job, but there wasn’t any indication of him having any psychological trauma to parse out. Any attempt to establish a lasting impact from the events of the first "Avengers" didn’t go on for long, as seen by how quickly Selvig recovered after "The Dark World."
Justin Hammer vowing revenge at the end of Iron Man 2
At the end of "Iron Man 2," weapons manufacturer Justin Hammer (Sam Rockwell), after giving away valuable information about Ivan Vanko’s (Mickey Rourke) big evil plan, is arrested by police officers. After initially resisting, Hammer is finally carted away by law enforcement. As this happens, he calls back to Pepper Potts and Black Widow (Scarlett Johansson) that this isn’t over and that he’ll be getting his revenge sooner rather than later. Perhaps that was originally the plan. MCU films don’t just keep any villain alive and well, after all. Keeping Hammer alive and thirsting for vengeance had to be thought of as a way to set up future installments.
However, for whatever reason, Hammer has not re-emerged in the MCU. "Iron Man 3" had no place for Hammer while other movies starring Tony Stark, like "Captain America: Civil War," also found no room for him. The most peculiar part of this is that Rockwell’s profile has increased substantially since "Iron Man 2" came out. Having won a Best Supporting Actor Academy Award and getting another Oscar nod in the same category, one would think Marvel Studios would be scrambling to bring him back. Instead, Rockwell’s entire presence in this franchise has been limited to "Iron Man 2" and a tiny cameo in the short film "All Hail the King."
Betty Ross and Bruce Banner’s relationship
In "The Incredible Hulk," viewers aren’t just introduced to the MCU incarnation of the unjolly green giant. They also get a first glimpse of the franchise’s version of the romance between Bruce Banner (Edward Norton) and Betty Ross (Liv Tyler). This is a relationship complicated by Banner watching out for his heart rate quickening, out of fear of turning into the Hulk. This dynamic was established as a crucial part of Banner’s life and was even used, through Hulk uttering the word "Betty", as a signifier that there may be more of Banner in the Hulk than there appeared.
However, Betty has never resurfaced in the MCU despite her father, General "Thunderbolt" Ross (William Hurt), managing to re-emerge as a recurring presence in recent entries in the saga. The character hasn’t even been referenced again, either by her father or by Banner. Instead, Banner took up a romance with Black Widow in "Avengers: Age of Ultron," which seemed to close the book on this initial love affair for the Hulk’s alter-ego. The only post-"Incredible Hulk" nod to the character in the MCU was through the initial codename for the Hulkbuster armor AI in "Age of Ultron" being Veronica, a nod towards the "Archie" character of the same name who had a rivalry with a lady named Betty.
Nick Fury going rogue at the end of The Winter Soldier
"Captain America: The Winter Soldier" ends with a genuinely nifty beat; Nick Fury opts to remain dead. After faking his death earlier in the film, one would expect Fury to just return to his regular day-to-day duties by the end of the feature. Instead, Fury makes the conscious choice to remain deceased to the general public. The viewer even gets a glimpse at his headstone located in a Washington D.C. cemetery. As Fury walks off-screen in "The Winter Soldier," the possibilities for what he could be up to next are limitless.
Strangely, then, "Age of Ultron" brings things right back to their original status quo. While initially Fury is depicted as someone who’s been off the grid for a while, he’s eventually shown to be manning a Helicarrier in his traditional leather garb to help Sokovian civilians get to safety. Rather than a shadowy individual believed to be dead by most, Fury is once again a public figure that everyone knows is alive and well. It’s a strange move that undercuts the ending of "The Winter Soldier" and all the narrative possibilities that Fury remaining dead could have brought.
Everything related to the planet Xandar
In the initial "Guardians of the Galaxy" movie, Xandar is an important planet. It’s where four of the five titular superheroes meet up, as well as home to the headquarters of the Nova Corps organization, and the backdrop for Ronan the Accuser’s massive final battle to execute his vengeance against the planet’s occupants. Given all that and the fact that it housed an Infinity Stone at the end of "Guardians of the Galaxy," fans might expect such a location and its characters, including Nova Prime (Glenn Close) and Rhomann Dey (John C. Reilly), to reappear throughout future MCU adventures, particularly cosmic-based ones.
Instead, the planet hasn’t reappeared at all in subsequent films. The Nova Corps gets name-dropped in "Guardians of the Galaxy Vol. 2" while Xandar also gets mentioned in "Thor: Ragnarok" and "Avengers: Infinity War." That’s the extent that this planet has factored into the franchise post-"Guardians of the Galaxy," with even its destruction as Thanos procured its Infinity Stone happening entirely off-screen. Xandar started as a seemingly important place but it’s been largely brushed aside in the mythology of the Marvel Cinematic Universe.
The fate of Bobbi Morse
Starting with the show’s second season, Bobbi Morse/Mockingbird (Adrianne Palicki) was a critical part of "Agents of S.H.I.E.L.D." and its ever-expanding mythology. However, she and her love interest Lance Hunter eventually left "S.H.I.E.L.D." in the third season episode "Parting Shot." In-universe, this was because the duo would be more dangerous to their S.H.I.E.L.D. comrades if they stuck around — they were forced to leave to keep Coulson and company safe. However, beyond these fictitious confines, Morse’s sudden absence was done to allow herself and Hunter to headline a spin-off show entitled "Marvel’s Most Wanted."
However, those plans hit a snag once ABC opted to pass on "Most Wanted," leaving the two characters in a state of limbo. Suddenly, it was uncertain where exactly Morse fit into the MCU, with the two failing to return to "Agents of S.H.I.E.L.D." as series regulars even after "Most Wanted" went belly up. Though Hunter managed to return in a guest appearance capacity in a later episode of "S.H.I.E.L.D.," Morse remained M.I.A. for the rest of the program’s run. Part of this appears to be due to scheduling conflicts for Palicki, who eventually found a lead role on the Fox sci-fi series "The Orville." However, no official reason has ever been given for her sudden departure. Whatever caused the character’s absence, a hole was left in the "Agents of S.H.I.E.L.D." mythology that kept all storylines related to Morse awkwardly unresolved.
What happened to Ghost?
For "Ant-Man and the Wasp," the two titular tiny heroes faced off against not Thanos, not He Who Remains, but rather Ghost (Hannah John-Kamen), a woman who can move through objects and constantly looks like she’s glitching in and out of reality itself. Ghost turned out to be a morally complicated figure, one who merely wanted to cure her condition, not destroy the world. While she wasn’t above doing bad things, she was also somebody whose life wasn’t defined by acts of malice.
A scene at the end of "Ant-Man and the Wasp" suggested that she and her surrogate father figure Bill Foster (Laurence Fishburne) would be sticking together for whatever came next. But Ghost has ended up being absent so far from the rest of the Marvel Cinematic Universe. Despite Ant-Man even name-dropping her during the mid-credits scene of "Ant-Man and the Wasp," Ghost has never appeared in another MCU entry. It also doesn’t look like Ghost will get her storyline resolved in "Ant-Man and the Wasp: Quantumania" — there’s been no news on John-Kamen getting cast in that film, plus she’s committed to starring in "Red Sonja."
The Scorpion’s thirst for revenge
In the middle of "Spider-Man: Homecoming," the young webcrawler’s inexperience with properly handling criminals is made apparent through the bungling of his attempt to stop a weapons sale on a ferry. This transaction involves the henchman of the film’s primary villain, Adrian Toomes/The Vulture (Michael Keaton), but it also entails Mac Gargan (Michael Mando) a criminal who, in the comics, is also known as the supervillain The Scorpion. Here, Gargan is depicted as just a person (albeit one with a scorpion tattoo on his neck) and one who quickly vanishes in the chaos of Spider-Man’s botched attempt to stop the crime.
The mid-credits scene of "Homecoming," in which a battered and vengeful Gargan confronts Toomes in prison and asks him if he knows the secret identity of Spider-Man, seemed to be setting up the idea of Toomes as a recurring threat to Spider-Man. However, Gargan has made no further appearances in either "Spider-Man: Far from Home" or other Sony/Marvel productions like "Venom." There has also been no word on him appearing in future productions like "Spider-Man: No Way Home," while a rumored presence in the feature "Silver and Black" went nowhere once that film got canned in pre-production. While Gargan was useful in showcasing Spidey’s inexperience in "Homecoming," the seeming lack of interest in further exploring the character indicates his usefulness in the MCU may have come to a close.