It's well known that when Dr. Bruce Banner gets angry, he turns into the Hulk , but what happens when the Hulk transforms into a Hulk of his own? Something nasty, and ultimately tragic.
Bruce Banner first transformed into the Incredible Hulk in 1962, with the character originally adopting a mean spirited attitude with serious anger issues. The Hulk eventually regressed in terms of language and speech, though when provoked the Hulk became a raging beast that would smash any opponents who crossed his path. Over the years, writers experimented with the notion of the Hulk manifesting in different ways, such as his "Joe Fixit" identity, a grey hulk who is very articulate, acts like a mobster, and is very strong. Many variations of the Hulk have become fan favorites, such as the "Professor Hulk" incarnation, recently seen in Avengers: Endgame, or the "World Breaker" incarnation from World War Hulk. While the current version of the Hulk, the "Devil Hulk," might seem like the most sinister Hulk of all, there is still one more beast lurking within the Hulk's own psyche.
This savage version of the Hulk made his first appearance during Marvel's Axis event in 2014, an event that affected heroes and villains alike. The villainous Red Skull had stolen the brain of the deceased Professor Charles Xavier and replaced his own brain with his. This allowed the Red Skull to access Xavier's mutant powers of telepathy. Though "Red Onslaught" proved to be too powerful for the combined teams to handle, Magneto, alongside an army of super-villains such as Sabretooth, Doctor Doom, and Carnage, joined the fight against the Skull and turned the tides in the heroes favor. Scarlet Witch and Doctor Doom end up casting a spell of inversion, an attempt to bring forth Professor X's personality inside the Skull's newly acquired brain.
However, while Charles Xavier's personality did return, the spell also "inverted" the personalities of all the heroes and villains on the scene. While heroes like Luke Cage and Iron Man were now villainous, and villains like Carnage were heroic, no hero has affected more than the Incredible Hulk.The Hulk had transformed from his large, green, and bulky form to a grey, white haired, red eyed monster dubbed "Kluh." Kluh being an inverted Hulk was born due to the Hulk's own rage, rather than Bruce Banner's rage, and was far from the gentle giant that Hulk normally is.
While the Hulk can be quite destructive to those who cross his path, he frequently wants to be left alone, and would much rather avoid humanity altogether, as most people seek to harm the Hulk. Kluh on the other hand seemingly relishes destruction, and actively sought to murder as many people as possible. Kluh showed no remorse attacking his teammates in the Avengers, and outright tried to eat Nova's arm at one point, showing how deranged this version of the Hulk truly was. Though the inversion spell was reversed by the end of the story-line, reverting Kluh back to the Hulk, it begs the question as to whether or not Kluh could ever re-emerge?
While the various incarnations of the Hulk are manifestations of Bruce Banner's psyche, Kluh is a manifestation of the Hulk's own psyche. One of the more tragic elements of Kluh is the fact that he was born out of the Hulk's own pent up anger and rage. The Hulk has endured a lot of hardships and turmoil in his lifetime, being constantly hounded and pursued by the military, as well as having fought against both Marvel heroes and villains alike. All of this rage, having been pent up for years, was kept in check by the Hulk, but the inversion spell was all it took to lower the Hulk's restraints and let Kluh loose.
The fact that Kluh had not emerged at any point prior to Axis is something of a miracle, as this form of the Hulk could do some serious damage if left alone for too long. This Hulk also shows just how much strength the character has been holding back over the years and that, if he were a villain, he could prove to be one of the most powerful threats in the Marvel Universe.
Though the Marvel Universe currently has its hands full with the Devil Hulk, who currently plots to destroy Marvel's entire world, it would be interesting to see Kluh reemerge. Perhaps there is something of a reluctant hero in Kluh, one who could emerge in the right circumstances or conflict. Whether he ever returns as a hero or villain, Kluh is one of the more tragic, and deadly forms that the Hulk has taken over the years.