WARNING: The following contains spoilers for The Immortal Hulk #33 by Al Ewing, Joe Bennett, Ruy José, Belardino Brabo, Marc Deering, Mark Morales, Paul Mounts, Nick Pitarra, Michael Garland and VC's Cory Petit, on sale now.
The Immortal Hulk has given us some of the deepest insight into the recesses of Bruce Banner's mind. As he wrestled with the supernatural Green Door and the One Below All, coupled with the emergence of the Devil Hulk and its subjugation of all other Jade Giants within Bruce's mindscape, bit by bit secrets started leaching out that not even the human side of Bruce could have remembered.
The Immortal Hulk #33 reveals Bruce's first kill and it's actually a very ominous moment -- because he didn't turn into the Green Goliath. Yet, it's a Jekyll and Hyde moment that made his body the perfect host for the Hulk.
Following Xemnu's brainwashing of the world, Bruce has been locked away and Robert Banner has emerged. He's basically the evil version of Bruce -- a look at what he'd be if he were allowed free rein. In Robert's eyes, he's maxing out Bruce's potential; this is clearly something Bruce tried to keep locked down, because the unhinged Robert is all about chaos and disorder.
When Samson and Dr. McGowan at Shadow Base pry into his mind to see if they can get the Hulk back, uncorrupted, so he can stop Xemnu, Robert indicates that's not going to happen. Bruce is a prisoner and when the book does shift to his mental cage, we see young Bruce watching Xemnu on TV, clearly enjoying the childhood he never had in real life.
Samson presses "Bob" about Xemnu rewriting his mind with false memories, but Robert reveals he knows exactly what's real and what's not. The mind-control happened to Bruce, not him; that's why he's free. This dark persona is mentally robust and is surviving Xemnu's psychic onslaught. He offers up a sample of how clear his memory is: A shocking moment where he recalls enjoying how he killed his own father.
In Marvel history, Bruce and David got into a tussle at the grave of his mom, Rebecca, because Bruce hated how abusive his dad was towards her. In the scuffle, Bruce tried to protect himself and used his feet to push David off, only for his dad to crack his head on her tombstone and die. The twist is, Bruce did it for spite. He enjoyed it and as "Bob" says, it was premeditated murder. The "dark and strange" persona of Bruce emerged: All human, all angry and knowing the repercussions.
So while Bruce has a gamma Hulk inside him, all these years he had a human Hulk too -- one that led to conflict and corrupted him to kill, although it's something Bruce readily accepted. It seems this allowed the Hulks to settle in Bruce's mind, body and soul neatly. It also explains why the ghoulish David has been haunting him thanks to the Green Door. Bruce feels some measure of guilt and his dad was apparently seeking revenge through mental torture. As for "Bob," it's obvious Samson and McGowan don't want him and the Devil Hulk getting into the pilot's seats of Bruce's body, because this will be the most destructive Banner/Hulk combination the Marvel Universe has ever witnessed.