Real Name: Artem Fedoseev

 Artem Fedoseev was a scientist who worked for the Soviet Union as a weapons designer.  He developed an explosive called the Zerobomb, which was designed to destroy 75% of the United States with a single warhead.

Feeling guilty for creating such a powerful weapon, Fedoseev stole the prototype and hid it somewhere in the Arctic Circle.  Hydra and the Avengers fought over the hiding place, which turned out to be a Soviet-era submarine.  Artem Fedoseev is presumed to be the skeleton found with the bomb on board the submarine.