The Uni-Power is one of Marvel's most powerful entities. An aspect of the Enigma Force, the Uni-Power chooses hosts across the universe and imbues them with cosmic-level power, and was recently revealed to be a counterpoint to the King in Black, Knull. The Enigma Force only remains bonded with someone as long as it chooses, before abandoning them to find a new host who can accomplish more good with that upgrade.
There have been numerous heroes over the years who've been briefly possessed with the cosmic power, including two of Earth-616's Spider-Men. Although neither hero got the chance to use the power for too long, this briefly transformed Spider-Man into a cosmic level figure. But could the power boost have worked out in the long run?
Peter Parker was imbued with the energies during the Acts of Vengeance crossover event, where multiple villains targeted heroes they didn't usually face off with in hopes of gaining an edge. It came at a crucial time for Spider-Man, allowing him to defeat the massive Tri-Sentinel in Amazing Spider-Man #329 by David Michelinie and Erik Larsen. Afterward, the cosmic force abandoned him for a different host. In Spider-Geddon #5 by Christos N. Gage and a host of artists, various Spider-Heroes from across the multiverse were united against the Inheritors on Earth-616. After summoning the Enigma Force, it was Miles Morales who was chosen as its host, giving him the strength to help lead the Spider-Heroes to victory over the Inheritors. After the battle concluded, the Engima Force left Miles behind to find a new host.
Considering the massive power boost that comes with the Captain Universe title, it's honestly something of a shame that the Spider-Men didn't get the chance to use it longer. Of all the heroes in the Marvel Universe, there are none that respect the creed of great power coming with a great responsibility than Spider-Man. Peter Parker or Miles Morales could have become a genuine Marvel Universe game-changer, imbuing one of the universe's single most powerful elements with a firm sense of morality and purpose. It could have elevated Spider-Man from the streets of New York to the entire cosmic scale of the universe.
Two case studies for this possibility occurred across the multiverse. What If...? #31 by Glenn Herdling and Scott McDaniel introduced a world where Peter never stopped being Captain Universe following his battle with the Tri-Sentinel. Using his newfound powers, Spider-Man defeated cosmic threats that endangered entire Avengers rosters. Although he eventually lost control of himself, Spider-Man's sense of responsibility led the Enigma Force to briefly cause world peace by connecting all of humanity as one. Another Peter retained the Engima Force and was introduced as a major figure in Spider-Verse by Dan Slott and Olivier Coipel, who'd largely brought peace to his world before being killed by the Inheritors.
It's a reminder that Spider-Man might be one of the few types of heroes who can find themselves with the power of the universe and still have enough sense of themselves to use those abilities responsibly. Spider-Man's adaptability and innate powers, along with the cosmic upgrade could have made Peter Parker or Miles Morales the Marvel Universe's most heroic cosmic force. But it would also be the ultimate refusal of Spider-Man's classic status as a friendly neighborhood hero, and cost New York City some of its most dedicated defenders. While Spider-Man got the chance to experience cosmic importance, it's probably a good thing the Spider-Heroes ended up more down to Earth in the long run.