The Incredible Hulk is Marvel’s go-to stand-in for Dr. Jekyll and Mr. Hyde. In whatever incarnation, there are two sides to his personality sitting in opposition to each other. The Marvel Cinematic Universe version based its incarnation largely on the 1970s TV show, complete with Edward Norton’s version of Bruce Banner conducting his experiments into gamma radiation that matches Bill Bixby’s character shot for shot. It's a quick way to codify Banner’s rage; a mild-mannered scientist who kept everything bottled up until it literally exploded in green.

That includes the unspoken presumption that unleashing the Hulk is to be avoided. His unthinking rage created chaos and destruction, which kept both Bill Bixby’s Banner and the subsequent MCU versions constantly on the run for fear of harming an innocent. But as one astute fan noted on Reddit, Bruce Banner can be far more terrifying than his unstoppable alter ego. And he proved it with just a single line.

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Loki is beaten by the Hulk

For most of Phases One through Three, the MCU treated Banner’s dilemma as that of two souls trapped in the same body. It informed the character’s arc during Avengers: Infinity War, when he faced Thanos as the Hulk and Banner, and lost each time. He’s able to reconcile his two halves for Avengers: Endgame – presumably providing the combination of power and control needed to undo the Snap -- but that also confirms a reality that the character can’t always acknowledge. The Hulk’s rage started with Banner, and existed long before his gamma experiments. The green monster was created from Banner’s own emotions.

That crops up during Mark Ruffalo’s first appearance as the Hulk in 2012’s Avengers. “That’s my secret Captain: I’m always angry,” he announces before transforming into the Hulk and setting up the team’s climactic counterattack against the invading Chitauri. It’s become a signature line for the character, as lost in the heroism of the moment is implicit acknowledgement that his anger fed this particular “Mr. Hyde.” Accepting and embracing it is the only way to control it, which Banner does in defense of New York with his fellow Avengers.

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Bruce looks up

The idea pays off in the next movie, Avengers: Age of Ultron, which the Reddit post referred to. In the moments leading up to the creation of Vision, the team seems as divided as ever on how to proceed. That includes the recent addition of Quicksilver and Scarlet Witch, who betrayed Ultron to the Avengers, but until very recently were the heroes’ tenacious foes. Wanda, having unleashed the Hulk to disastrous effect earlier by getting inside Banner’s head, becomes the specific focus of his ire. “I could choke the life out of you and never change a shade,” he tells her coldly.

Among other things, it demonstrates the extent of Banner’s control over his anger – control he worked very hard to achieve and which Wanda undid more or less with a wave of her hand. And to express his anger in such calm, passive terms is truly unsettling. Even worse are the circumstances they find themselves in, with Ultron building a presumably unstoppable new body and every delayed second making a difference. Banner will happily waste that time to threaten her, and his tone sounds anything but idle.

It’s also an indication that he shouldn’t be dismissed. As large as the Hulk looms in everyone’s minds, Banner reminds the room where the anger that created him comes from. He doesn’t need powers to kill her and he doesn’t need to lose control to do it. As destructive as the Hulk can be, it’s indiscriminate – closer to a storm or a force of nature than an act of will. Banner’s line speaks of being able to do far worse with his will intact. The MCU likely has more stories to tell with the figure. His chilling certainty in this moment suggests that not all of them will be bright.

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