The following contains major spoilers for Thor #26, available now from Marvel.
The Marvel Universe has seen some truly explosive battles over the years, often between powerhouse figures of incalculable strength. While these fights are almost always the source of great spectacle, the havoc wrought in the process is just as astounding. In the case of the latest rematch between the God of Thunder and the Incredible Hulk, the collateral damage might be even more shocking than every other development. Especially now that it has left Asgard effectively cut off from every other realm.
Over the past months, the lives of both Thor and the Hulk have devolved into tragedy. For the former, Odin's death and imprisonment within Mjolnir have created a sense of anxiety. And, in the case of the latter, the Hulk's personal demons have driven his human alter-ego to seek exile out in the Multiverse. Of course, it wasn't long before the paths of these two crossed. Their battle not only resulted in a Hulk-like God of Thunder, but Thor #26 (by Donny Cates, Martin Coccolo, Matt Wilson, and VC's Joe Sabino) saw consequences of divine proportions.When Sif attempted to bring Thor home via the Rainbow Bridge, the irradiated Asgardian did the unthinkable by destroying it entirely.
The Bifrost was first seen alongside Asgard's own introduction in the 1962 Journey into Mystery #85 story "Trapped by Loki, The God of Mischief" (by Stan Lee, Larry Lieber, and Jack Kirby). Also known as the Rainbow Bridge, the Bifrost is the ancient path from Asgard to the rest of the Ten Realms. The Bifrost was guarded by Heimdall the All-Seer for years before Sif took up his place. Though the Bifrost has been destroyed previously during the events of 2004's "Ragnarok," that took a series of coordinated assaults and prior damage to make possible.
Now that Thor has shown off just how powerful he is in his radioactive new form, the question of what can stop the Hulk is becoming more of a necessity than a cry for justice. With everything at his command, the All-Father is surely capable of a lot more than just breaking the Bifrost. If he decided to point his rage an any Realm in particular, there may be no way to stop him from eradicating it. Considering his current state, it's hard to imagine he would ever make such a calculated move, though him following his instincts instead hardly makes the situation any better.
Assuming Thor is simply reacting to whatever is happening around him, that might have already set him on a collision course for Asgard. Even without the Rainbow Bridge, the God of Thunder still wields impossible power. It's likely that he could make that trek entirely on his own with little to no hurdles to slow him. If anyone else were to get involved, they would only be delaying the inevitable at worst, or at best redirecting Thor's rage. On the other hand, that may be the only chance left of staving off the impending threat.
Without the Bifrost, Asgard can only attempt to fortify itself rather than evacuate or mount a counter-offensive of any sort. But if another party were to intervene, they could very well draw Thor's attention towards a more suitable target, or trap. Banner is already fully aware that the perfect place for out of control Gamma Mutates exists in the void of the Multiverse. Despite the objective cruelty of subjecting anyone to that fate, a Hulk of Thunder is starting to seem like an awfully good reason for it.