The Incredible Hulk is well known for the curse of his powers - but in the case of his wife Betty Ross, that curse is flipped. When Bruce Banner's anger gets the better of him, he transforms into the giant Hulk, with super-strength, imperviousness to most weaponry, and a power level that is directly tied to his level of anger. But Defenders #2 reveals that Hulk is not the only super-strong hero in the Marvel Universe with power tied directly to emotions.
While the source of Bruce Banner's power was always stated to be immense levels of gamma radiation caused by a gamma bomb, the exact nature of his powers has varied ever since his origin in The Incredible Hulk #1 in 1962. Initially, the grey Hulk could only transform at night (and he was far more eloquent than his current comics version). As time passed, his transformations were tied directly to his anger (and in the 2008 The Incredible Hulk MCU film, his heart rate) - and readers learned that Bruce Banner was not the only Hulk.
Both the Red Hulk (later revealed to be Thunderbolt Ross) and She-Hulk (Jennifer Walters, Banner's cousin) would appear in Marvel Comics with similar powers. But a second Red Hulk turned out to be Bruce's wife at the time, Betty Ross. Her powers were quite different, as seen in Defenders #2 in 2012. When the team is trapped in a cell after an attack gone wrong, Betty hatches a plan to escape. She's reminded that the bars are made of enchanted metal from beyond the Earth, but that doesn't deter the Red Hulk. "When Bruce was possessed by that thing - it changed him. ... I got scared and...and I Bettied-out. Turned human again." She then insists that the team scare her so she can transform into her human self and slip through the bars.
Unlike Bruce Banner, Betty doesn't actually want to turn human again. This is perhaps in part due to the fact that she retains control of her actions while in her Red Hulk form. Contrast this with Banner, who has spent years searching for a way to rid himself of what he believes to be the "monster" - and even when he manages to live in peace with the Hulk, the two are separate entities with entirely different personalities, similar to Moon Knight but not entirely.
The Hulk is associated with anger and the negative aspects of losing control of one's emotions. Betty's Red Hulk, in this instance, associates anger with control, and only by being frightened is she able to (perhaps unwillingly) transform back into her human self. Every character suffering from a Hulk-like transformation is controlled, willingly or otherwise, through emotions and the pain that each of them bring.