WARNING: The following contains major spoilers for Heroes Return #1 by Jason Aaron, Ed McGuinness, Mark Morales, Matthew Wilson and VC's Cory Petit, on sale now.
In the world of Heroes Reborn -- a reality rewritten by Phil Coulson and Mephisto to transform the Marvel Universe into a new form -- most of the classic Marvel heroes never got the chance to exist. Instead, the Squadron Supreme was the chief protectors of the world, resulting in a glossy reality with a rotten ruthless core. In many ways, the Heroes Reborn took inspiration from concepts typically utilized in DC Comics and twisted them into dark new takes on classic Marvel ideas.
This includes Hyperion, the Squadron's powerhouse and "moral leader," who stands in as a substitute for DC's Superman. He's gained a number of fun elements that reference this over the course of the series, but perhaps the most important occurs in Heroes Return when it turns out that he even has his own version of Kryptonite -- and that it's a major element from the Marvel Cinematic Universe.
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Across the course of Heroes Reborn, Blade -- who remembers the way reality is supposed to be -- finds himself recruiting a new Avengers roster to contend with the Squadron. Traveling the world, Blade ends up adding Captain America, Thor, Black Panther, Echo -- who recently became the new host of the Phoenix Force -- and Starbrand. Rallying in Wakanda, they lure the Squadron into a battle that the latter team has no real chance of winning. The members of the two teams quickly square off, leading to a number of one-on-one fights. This includes Hyperion throwing down with Thor, perhaps the only member of the newly reassembled Avengers who has a hope of matching him in sheer strength. But as the fight goes on, Hyperion realizes that his punches are increasingly doing less and less damage to the Thunder God.
Hyperion begins to feel pain in ways he hadn't previously, and realizes that it's something about Wakanda that's draining his power. Slamming Hyperion further into the Earth, Thor cracks the Earth and reveals a massive deposit of Vibranium crystals -- which continue to severely weaken Hyperion. During a brief lull in the battle, Hyperion moves to help Nighthawk fight against Blade. Nighthawk reveals that the radiation that emits from Vibranium is actually, in this reality, the last remaining chunks of Hyperion's homeworld. The radiation emitting from the metal will specifically hurt Hyperion the longer he's exposed to it, eventually even killing him.
It's a fitting role for Vibranium (which prominently appeared in Black Panther) to have in the world of Heroes Reborn, effectively becoming the Marvel Kryptonite. The DC substance is the radioactive remains of Krypton, Superman's home planet. Drifting through space after the destruction of Krypton, the various crystallized forms of Kryptonite have a number of different effects on Superman. However, the most common form of the substance -- Green Kryptonite -- is highly toxic to Kryptonians and is perhaps the only surefire way to kill Superman and ensure that he stays down. Like Kryptonite, Vibranium came to Earth in the form of a meteor, crashing into the world and giving the humans smart enough to identify it the ability to fight back against one of their world's most dangerous figures.
While there are some key differences between the Heroes Reborn Vibranium and DC's Kryptonite (such as how Vibranium is still a viable metal for Black Panther to weaponize instead of just a crystal and that it doesn't appear to have any negative radioactive effects on humans, as Kryptonite can eventually have), it's still a perfectly clever way for Marvel to give their own Superman his own version of the original's greatest weakness.