Radioactive Man is a radiation-based Marvel character.
When the Radioactive Man fought Iron Man, Thor, and Black Panther inside the Stark Tower, he nearly bested them all until when he tried to absorb the Arc Reactor's power, he was defeated by the trio.
He was taken to the Negative Zone and helps out during Assault On 42 when Annihilus attacks the prison. He was seemingly killed by the annihilation wave.
At some point, Radioactive Man was apprehended by HYDRA and placed in a radiation-proof capsule in order to be used as a power source. Crimson Dynamo had obtained the key to the capsule so that Winter Guard could free them. When the destabilized Russian facility threatened a nearby village and the Avengers worked with the Winter Guard to save the village, Crimson Dynamo and Falcon freed Radioactive Man who then dissolves the facility.
Powers and Abilities
Radioactive Man possesses the power to absorb almost any kind of radiation from the environment around him and store it in his body's cellular structure. If needed he can release the stored radiation in blasts of heat, force, or pure radioactivity from his hands.
He can absorb and expel radiation across the spectrum, from heat blasts to high-intensity bursts that can rob objects of their inertia (stopping Thor's hammer in mid-flight). He is super-strong, and highly resistant to damage.
There is a superhero on the Fox animated sitcom The Simpsons that is also called Radioactive Man . But, the shared name is pure coincidence.