Dillon was a criminal who underwent illegal genetic experiments carried out by Dr. John Skrtic on behalf of industrialist Justin Hammer, who was competing with Osborn Industries to win a lucrative government contract to create a super-soldier serum. Having been successfully given electrical abilities, Electro, as he now liked to be called, was sold into the service of the Kingpin of Crime, Wilson Fisk, in return for construction contracts for another of Hammer’s projects. Electro served Fisk willingly as an enforcer, and when Spider-Man broke into Fisk Tower, the Kingpin set his new acquisition the task of taking the intruder down, something Electro swiftly managed. Electro was subsequently present when Kingpin murdered Frederick Foswell, the underboss known as Mr. Big, for having supplied Spider-Man with information.
When Spider-Man returned to the Tower a few days later to steal the surveillance footage showing Fisk’s crime, Electro and the Enforcers were sent to stop him. Initially dodging Electro’s blasts, Spider-Man then tricked his foe into stunning Ox, one of the Enforcers. After taking down the other two Enforcers, Spider-Man grappled with Electro, then threw him in to a stream of water coming from a broken water pipe, causing the electrical criminal to short out violently.
He awoke three weeks later in hospital to find that the Kingpin had fled the country and F.B.I. agents waiting for him to wake so they could question him as to his reasons for being in the crime lord’s basement. Electro’s killed everyone in the room and fled, but he was swiftly recaptured by Captain America, Iron Man and the Black Widow. He was imprisoned in a secure S.H.I.E.L.D. facility alongside several other genetically modified criminals (Doctor Octopus, Green Goblin, Kraven and Sandman), his powers blocked by a high-tech control collar, to be studied and interrogated by Hank Pym (Giant Man). After several months, Dr Octopus engineered a break out, and the group slaughtered their way to freedom, killing 35 S.H.I.E.L.D. agents on their way out. Their next move was a direct assault on S.H.I.E.L.D.’s Triskelion main base to capture Spider-Man, who had been moved there for his own protection. Octopus breached computer security to shut down the base’s defenses, then Electro overloaded both primary and back-up generators. The group entered and left equally swiftly with their objective.
Spider-Man was coerced into working with them on as they launched an attack on the White House itself. Conventional forces fell before them in seconds, but their progress was halted on the front lawn outside the Oval Office by the arrival of the Ultimates. Electro attacked Thor, and their battle raged into the air; but Electro’s powers proved no match for the alleged God of Lightning, who soon won the day, and along with his teammates, Electro was returned to custody.
Bolivar Trask hired Electro to test Eddie Brock and the Venom suit by leading him on a chase through Manhattan. Spider-man showed up, but was knocked unconscious, resulting in a battle between Venom and Electro for the life of the web-slinger. Although Venom defeated Electro, S.H.I.E.L.D. intervened before anything more could happen. Electro was then placed back into their custody.