Major spoilers for Spider-Man: Brand New Day follow.
Jean Grey appears to trigger the return of Savage Hulk in Spider-Man: Brand New Day, but she does not create him. The movie shows Jean inside Bruce Banner's mind, using Hulk against Peter. Bruce forces her out, loses control, and the angry version of Hulk takes over. Jean pushes him past his limit; the personality was already there.
That distinction clears up one of the movie's messier moments. Bruce has spent years as Smart Hulk, the version who combines Banner's mind with Hulk's strength. He reached that form before Avengers: Endgame and appeared comfortable with it through She-Hulk. Brand New Day does not explain his full mental history, but it shows that the balance is less secure than Bruce believed.
Savage Hulk is the older, more dangerous version most viewers remember from the first Avengers movies. He acts through anger and instinct, speaks less, and is much harder to reason with. When he returns, Peter is not facing the calm hero who can discuss a plan. He is facing Bruce's rage without Bruce firmly in control.
Jean Pushes Bruce Past His Limit
Jean breaks into Damage Control and takes control of Hulk before Peter arrives. Bruce fights her from inside his own mind and eventually throws her out. Peter warns Jean that she should not be digging through Bruce's head, and the warning is quickly proven right. Bruce wakes confused, becomes more aggressive, and changes into Savage Hulk.
The scene does not show Jean pressing a hidden switch or choosing a specific Hulk personality. She is trying to control a powerful mind that already contains years of anger, trauma, and conflict. When Bruce resists her, that mental fight damages the control he had built as Smart Hulk.
GamesRadar's ending recap describes Bruce as unable to think clearly after Jean leaves his mind. That is the clearest clue in the film. Savage Hulk returns because Bruce's control collapses at the worst possible time, not because Jean invents a new form or gives him new powers.
