Hulk

Bruce Banner was a scientist who was working on a gamma bomb when he noticed teenager Rick Jones out on the test range. Although he rushed out into the test site and heroically pushed the boy into the protective trench to save him from the blast, Bruce was exposed to extreme amounts of gamma radiation that altered his DNA structure due to gamma rays and trauma passed down by his father and caused him to become a giant green (at first grey) monster of incredible power known as the Hulk whenever he starts to get enraged.