What Happened To Every Version Of The Hulk?
9. Kluh
As the backwards name suggests, Kluh is the opposite of the Hulk, describing himself as the 'Hulk's Hulk' - a terrifying and vaguely sleazy version of the creature, powered by his intent to wipe out mankind.
Kluh is brought out during the events of Avengers & X-Men: AXIS, which sees the Avengers have their moral compass inverted, resulting in them becoming a bunch of villains. While it'd be easy to presume that Kluh was merely the result of this inversion, his dialogue suggests he's been around for some time, suggesting that this could be another persona that Banner has kept hidden as a result of the damage it could carry out if freed.
As such, chances are Kluh is also lurking in some shadowy spot of Banner's mind, where he will hopefully remain indefinitely.