Robert Hunter was born in Scranton, Pennsylvania. He was an electrical engineer. Due to genetic alteration carried out on him by the Kree Lunatic Legion, Robert gained the ability to explode and reform himself at will and became a professional criminal. Some time later, he exposed Captain Marvel to a carcinogenic nerve gas; this encounter ultimately caused Captain Marvel's fatal cancer. Since then he has clashed with Earth's superhumans, who have found creative ways to defeat him, including using the "fractioning (separation) of his exploded mass" against him (essentially, if he can't reform himself after an explosion, he can't explode again).