Justin Hammer is an unscrupulous industrialist and head of various international design and manufacturing firms. A long time competitor of Stark (now Stane) International, Hammer became one of the leading weapons suppliers in the world after Stark International moved out of weapons production. Hammer maintained other manufacturing interests besides weapons and it was while bidding for an electronics plant to be built within the borders of the small Communist country of Carnelia that Stark and Hammer came into direct conflict. Knowing that Iron Man was an essential part of Stark International's image as well as security (but not knowing that Iron Man was actually Anthony Stark), Hammer directed his engineers to develop a means to override Iron Man's armor. The engineers eventually built a hypersonic device able to breach the armor's refractory coating. Over a period of weeks they tested their ability to override the cybernetic circuitry of the armor by activating various weapons systems against Iron Man's will. Iron Man dismissed these incidents as mechanical malfunction rather than a deliberate override. Finally Hammer activated Iron Man's repulser unit, causing Iron Man to kill the Carnelian ambassador to the United Nations. His armor impounded, Tony Stark tracked the reclusive Hammer to the Mediterranean Sea, where he was taken captive by Hammer's mercenaries. There he learned about Hammer's designs upon him as well as some of his shadier operations such as the financing and outfitting of various costumed criminals in exchange for fifty percent of their profits. Stark managed to wreck the device that could override his armor and then donned his spare suit in time to battle Hammer's reserves, a small army of powerful costumed criminals. Vanquishing them, Iron Man damaged Hammer's floating villa and captured the man who designed the equipment that overrode his armor. Justin Hammer managed to escape. Although Iron Man managed to clear himself of the murder charge by exposing certain of Hammer's activities, he could not effectively thwart Hammer's operations, since his diverse corporate holdings are unknown to the authorities. Iron Man encountered Hammer a second time when he kidnapped Stark's girlfriend Bethany Cabe and brought her aboard his huge submarine. Iron Man managed to severely damage the vessel but was unable to apprehend Hammer.
Justin Hammer remains at large, a reclusive billionaire overseeing various international business interests, legal and otherwise. Among the many costumed criminals whom he has outfitted and financed operations for are Blacklash, Blizzard, Melter, Man-Killer, Beetle, Spymaster, Leapfrog, the Porcupine, Water Wizard, Stilleto, Discus, the Constrictor, Blue Streak and Captain Barracuda. Among those one of Hammer's companies has built weaponry for are the Orb, the Viper, and the Black Spectre and Zodiac criminal organizations.
