Robert Bruce Banner was irradiated with radioactive particles after the Gamma Bomb detonated. He was not killed but it caused him to frequently transform into a vastly powerful humanoid monster. At first, Banner changed into Hulk at sunset and reverted to human form at dawn. However, Banner’s body changed so that his transformations were triggered by the release of adrenaline when he became intensely excited no matter what time it was. Hulk is one of the most powerful beings and capable of matching the power of beings like Sentry and Thor. His strength is virtually limitless. Regardless of his size, Hulk has strong legs that allow him to run at speeds that are far beyond the natural physical limits of even the finest human athlete. It’s been shown that Black Panther’s claws and adamantium are capable of piercing Hulk’s skin but the damage is almost immediately regenerated.
The HULK, by Richard Williams.