There exists in the Marvel Universe a team of characters made up of analogues to Superman, Batman, Wonder Woman and the other mainstays of DC Comics' A-list. They have almost always been written as more abrasive than the heroes that they're copies of. But the newest version of the Squadron Supreme crosses a line that the Justice League would never step over.
For about four decades, various iterations of Hyperion, Nighthawk, Power Princess and Dr. Spectrum have been stand-ins for Superman, Batman, Wonder Woman and Green Lantern. Along with analogues for the Flash, the Atom, Firestorm and others, they have assembled into a conglomerate called the Squadron Supreme, usually acting as allies or enemies for the Avengers.
Past versions of the Squadron Supreme were used as vehicles for creators to explore some of the existential bugbears that hover around the concept of superheroes. You know, the "why doesn't Superman solve all the world's problems" kinds of questions. The 1985 maxiseries by late Marvel editor Mark Gruenwald, Paul Neary and others tackled the idea of how metahumans could impact the real world head on, showing the Squadron doing things like curing cancer, ending world hunger and stopping crime on a psychological level. That series ended in one big tragedy. The newest Squadron Supreme is spawned from several tragedies on a much bigger scales, as the team is made up of characters who are the only ones left from their native dimensional planes.
In the months before the publisher's big Secret Wars event, entire realities have been dying across Marvel Comics' multiverse. Hundreds of Earths were crashing into each other as a result of the machinations of the ultra-powerful Beyonders and, as chronicled in the New Avengers series, a consortium of elite superheroes tried to save the mainline Marvel reality from suffering the same fate. But their methods became increasingly desperate and morally questionable, culminating in the death of Earth-4290001 at the hands of Namor the Submariner. Then all of existence seemingly ended, only to be saved in the 11th hour by Doctor Doom.
The ongoing Secret Wars series showed that Doom snatched the Beyonders' power and cobbled together a patchwork planet from various realities. Marvel's current publishing initiative is unspooling the omniverse that comes after Secret Wars. But Squadron Supreme #1 -- written by James Robinson, with art from Leonard Kirk, Paul Neary, Frank Martin and Travis Lanham -- is very much concerned with events from before the reconfiguration of everything. This Squadron has vowed to protect the Earth by any means necessary and counts amongst its number the Spectrum from Earth-4290001. The entire team agrees that Namor needs to pay the murder of her home planet.
What follows is an attack on Atlantis...
... which Hyperion lifts from under the sea and smashes into a desert.
Some Atlanteans escaped the carnage but that's not the punishment that the Squadron has in mind for Namor. What they do is much more severe.
This act of vengeance sparks reactions all over the world, with people praising or condemning the Squadron for their actions. Killing a major superhero puts them on SHIELD's radar, too, with at least one former superpowered teammate of Namor's vowing to shut the Squadron down.
Even with superhero death pretty much being a revolving door, it's not a small thing for Marvel to kill the Sub-Mariner. He's the oldest character in the publisher's stable and encapsulates much of the appeal in Marvel's approach to superhero construction. As either a hero or a villain, Namor was brash and imperious, doing seemingly whatever he wanted to serve the ends of his royal station. He was consistently transgressive throughout his publishing history -- saltier in language and affect, more cocky and pompous in combat -- when compared to Superman or his other chronological peers. Namor was edgy even before edgy was a thing. And now the character's come against the business end of the notional blade he helped sharpen, getting beheaded by a team designed to be even more transgressive in attitude than him. The stakes are likely going to get even higher as this series goes on and it will be interesting to see when it all starts to feel like too much.