Mallen's parents were killed during an FBI shootout that involved charges of weapons violations, causing him to grow up with a deep mistrust and hate of authority, and the US government in general.
Major Story Arcs
Later, Mallen having become bitter, joins a small terrorist cell. The members were given the Extremis drug by Maya Hansen and Aldrich Killian. Mallen consumed this drug, and upon gaining the superhuman abilities that it afforded him, decided to get revenge on the FBI and the government. Mallen attacked the FBI branch in Houston. There he was confronted by Iron Man and after a short battle, injured the aforementioned hero, but was forced to retreat due to police presence. He also threatened to kill the U.S. leaders in Washington D.C., and after nearly killing Iron Man, decided to make his way there, killing a protestor for having different opinions on the way. Meanwhile, after recovering and gaining similar abilities himself, Iron Man evacuated D.C. in preparation for their final battle. After ambushing Mallen, Iron Man used his Extremis-enhanced suit to beat Mallen down. However, in a last display of anger and defiance, Mallen came back and started strangling Iron Man, forcing him to shoot a hole in Mallen's chest with his unibeam, and then decapitate him with his repulsors, killing him.
Powers & Abilities
Due to the mutation that resulted by consuming the Extremis drug, he gained a multitude of superhuman abilities, including super-speed (allowing him to move in excess of 200mph), super-strength that allows him to easily pick up cars and crush the Iron Man armor with his bare hands, incendiary breath, the ability to give of bursts of electricity, enhanced agility and stamina, durability enough to withstand a blast from the Iron Man's unibeam at 80%, claws on his hands, and enhanced regeneration, enough to allow him to fully regenerate after being shot several times.
Mallen appears in Iron Man: Armored Adventures episode "Extremis". Unlike the comics, he is instead a low-ranking S.H.I.E.L.D. agent who is fired for his mental instability, and steals and injects himself with the Extremis formula, becoming a superpowered maniac and going on a vengeful rampage. Mallen injures Stark and forces him to also take Extremis, allowing him to defeat Mallen.
Mallen is one of the characters that is part of the composite of Aldrich Killian in Iron Man 3. Killian displays many powers similar to Mallen's, including super-strength, speed, reflexes, regeneration and durability. This version of Extremis allows the user a certain degree of pyrokinesis, granting them the ability to superheat parts of their bodies to 3000 degrees Celsius, and Killian makes use of the fire-breathing ability at one point in the film.