WARNING: The following contains spoilers for The Immortal Hulk: Great Power #1, written by Tom Taylor and art by Jorge Molina, in stores now!
The Hulk is the strongest there is, being the absolute zenith of superhero potential. The few who can endure his wrath for more than a few seconds before crumbling under his flurry of blows rank among the strongest in the universe, such as Thanos, Galactus, or Odin himself. However, fans can now add a surprising combatant to those who have conquered the Hulk: Loki.
The God of Mischief might not be the strongest supervillain on the planet, but he's certainly able to conjure power that can subdue and stop the Hulk in mere seconds. In The Immortal Hulk: Great Power, a fight breakouts between Spider-Man, Hulk and Loki that lasts a single page. Here's how Loki won, and what his victory cost.
HULK VS. LOKI
The fight, if you can call it that, lasts seconds. Loki regards the Hulk as a danger to society, and, because the God of Mischief is attempting a heel-face turn in order to become a hero, he decides to defeat the Hulk. Of course, even despite his Asgardian strength, Loki is no match for the Hulk so he doesn't bother using his strength to subdue the beast. He manages to use something else.
Loki realizes he can't beat or trick the Hulk so he does something a little different: he rips the gamma radiation out from Hulk. However, due to the way magic works on Earth, there is an equal opposite reaction. The Hulk leaves his body and deposits itself in Spider-Man. This leaves both of them overwhelmed and unconscious.
The reason Loki can do this is that he uncovers the source of the Hulk's power. Now that the Hulk is articulate, Loki can determine that the source of the Hulk's power is energy -- specifically, gamma radiation. Because of this, he can use his magic to control and manipulate it.
Loki's plan leads to an obvious problem, of course: Spider-Man becomes the Hulk temporarily. It's only thanks to the Fantastic Four that Spidey is subdued. When they confront Loki about the obvious problems with what happened, he resolves that if he were to try to fix Spider-Man up, it would only cause even more mischief. So clearly Loki is able to stop the Hulk at the moment, but the beast will always return.
Of course, Spider-Man learns how to use gamma radiation to purge the Hulk from his system and place it back into Bruce, but this doesn't change the fact that Loki effectively purged the Hulk from existence.
EARTH LAW VS. SPACE LAW
Loki complains that the Earth's laws of physics resulted in Spider-Man receiving the gifts of the Hulk, but what if the playing field were different? It's hard to say, but this statement does indicate that, were Loki and Hulk fighting on a playing field more magically focused, it's possible that the Hulk would've been left completely powerless and beaten.
This means that, in some places, magic can render the Hulk completely defeated. So, by that logic, someone, like Doctor Strange or Dormammu who can transfer people into new realities, could use magic to strip the Hulk of his powers. The energy would disburse into the ether, never to be seen again.
HULK'S TIES To MAGIC
This clearly means that magic is in some ways linked to the Hulk. The bizarre element here is that Loki can only sense that the Hulk's power is tied to radiation because the Hulk has grown in recent years more intelligent. In a bizarre way, the more refined the Hulk, the more refined the power source.
So, can another magic user like Loki manipulate the Hulk? Fans have seen the Hulk square off against some pretty powerful magic users, like Doctor Strange or Mephisto over the years. This means that literally any of them if they deliberately applied their powers, could rip the Hulk out of Bruce and place him into someone else. For an organization like Weapon Plus, this prospect might appear very tempting, since it's their objective to create super soldiers, and they already have tried to recreate the Hulk with Weapon H.
The events of Immortal Hulk, which has left the Hulk articulate and self-aware, have left Bruce and the people in his head more vulnerable to magic. This could mean that the Hulk's more calm mentality makes him more aligned with magic. If that's the cast, in theory, the Hulk could learn to control and meditate his abilities in order to combat magical attacks.
The Hulk better get a grip on his magical potential and vulnerabilities, however, and fast. If someone stripped the Hulk of his powers once and put it into someone else, they can do it again. And Hulk is in confrontation with the One Below All, a demonic force well attuned to the magic Loki just used. If the One Below All wishes to stop the Hulk, he now has the means to do just that, all thanks to the God of Mischief being reckless.