The Marvel Cinematic Universe has expanded too far to be able to account for every character nowadays, so it’s only natural that some will fall through the cracks. Some heroes receive a big funeral, while some vanish without a trace, even if they have universe-altering powers.
White Vision

This new, remade Vision was introduced in WandaVision and recalled everything that the original synthezoid had. He then proclaimed himself the “one true Vision” and flew away from Westview, and no one knows where he is now.
G’iah

Talos’ daughter, G’iah (Emilia Clarke), would by the end of Secret Invasion have incorporated the DNA of almost every Avenger and cosmic being, making her the most powerful being in the universe. After all, she has god-level powers, but hasn’t been seen or mentioned since!
Dane Whitman (Black Knight)

Eternals took care to make it clear that Kit Harington has been handed the ancient curse of his family and the power to wield the Ebony Blade as well. Dane’s superhero journey has been put on ice, despite a post-credits scene in which a voice (Blade) warns him of the sword.
Starfox (Eros)

Another big Eternals cliffhanger saw the introduction of Harry Styles as Eros, the powerful biological brother of Thanos, who was an Eternal. Starfox used the cosmic power to wield emotions to embark on a mission beyond the confines of Earth, but has not met our heroes since.
Hercules

A mid-credits sequence of Thor: Love and Thunder introduced the real Greek Demigod Hercules (Brett Goldstein), who was sent by an angry Zeus to hunt down the God of Thunder. Despite the promise of the giant mythological battle, Hercules has disappeared from the actual slate.
Dr. Leonard Samson (Doc Samson)

But even before Modern Family, Ty Burrell was Bruce Banner’s psychiatrist friend in the 2008 film The Incredible Hulk. In Marvel continuity, Samson is transformed into a gamma-powered superhero and is given superpowers, but unfortunately, the MCU abandoned his character arc at the end of Phase 1.
Quake (Daisy Johnson)

Daisy Johnson became a powerful earthquake-making inhuman warrior as a prominent hero of ABC’s Agents of S.H.I.E.L.D. Other street-level and TV heroes are officially in the main-line movies, but Quake just isn’t a part of the deal.
The Stakar Ogord Ravager Crew

Guardians of the Galaxy Vol. 2 brought together an elite and ultra-powerful bunch of classic cosmic heroes like Stakar Ogord (Sylvester Stallone), Aleta Ogord (Michelle Yeoh), Krugarr, and more. Other than a short cameo by Stallone in Vol. 3, this tremendous cast hasn’t been involved in the larger cosmic MCU.
Skaar

She-Hulk: Attorney at Law left a big bomb by announcing that Hulk has a teenage son named Skaar, and he was born on Sakaar. With his half-Hulk blood, Skaar is physically powerful beyond the imagination, but despite this, he was completely ignored in other projects as soon as he was introduced.
Nova Prime (Irani Rael)

Irani Rael was a strong leader of the Nova Corps, a highly capable interstellar military empire. Thanos apparently destroyed Xandar off-screen before Avengers: Infinity War, but whether he managed her survival or not and what will happen to the Nova Empire in the future remain unmentioned.