While it’s true that most iterations of the Hulk depict him as Bruce Banner’s scientifically personified anger issues, there’s at least one version of the story that supports this Redditor’s fan theory. In 2000, Marvel Comics introduced the Devil Hulk, and he’s exactly what he sounds like. Bruce encounters the literal demon in his mindscape, a soul plane littered with struggling Hulk personalities. This version of Bruce contains many Hulks inside him, each fashioned to cope with a different trauma from his childhood, and sometimes they fight because comics are weird and beautiful that way.
Devil Hulk is a proud, vengeful creature, who renames himself the Immortal Hulk after his first victory over Bruce’s numerous Hulk personas. Unlike his other personalities, though, the Immortal Hulk does not originate from within Bruce. He is a denizen of the Below-Place, which isn’t a euphemism for the Christian Hell because it is canonically lower in the bedrock of reality than the biblical realm of fire and brimstone. Bruce is connected to this malevolent domain by the Green Door, a portal he tore into existence when his gamma bomb project went sideways.
This version of Bruce’s story deals heavily with demonic possession because both the Immortal Hulk and the One Below All, the Below-Place’s deity, use the Green Door to control Gamma Mutates like Bruce.
