William Cross joined the CIA with the intent to learn the secrets of the trade and to make contacts which might one day prove useful to him. He intended to use CIA training and knowledge to obtain a profit for himself.
Specializing in information gathering and extraction, Cross worked with scientists within the organization to develop an effective method of brainwashing using ultrasonic technology. There he became romantically involved with Rozalyn Backus and met fellow CIA agent Marc Spector (Moon Knight).
Quitting the CIA soon after, Cross used his skills and resources to begin a number of highly profitable criminal operations including drug trafficking, extortion, and assassination. Assuming the codename Crossfire, he diverted a portion of his profits to hire a small army of mercenaries to serve as his enforcers. Crossfire's new goal was to sew the seeds of disorder and subversion within society in order to make a profit.
At one point in his career, some of his enemies booby-trapped his headquarters. The ensuing explosion robbed him of his left eye and ear, plus 85% of his hearing. He replaced his losses with cybernetic equipment. Crossfire eventually located the men who had injured him and eliminated them personally. William Cross (Earth-616).
Crossfire eventually decided that the existence of superhuman crime-fighters posed a threat to his operations. He poured his monetary resources into the refinement of ultrasonic brainwashing technology, with the aim of brainwashing all superhumans into battling one another to the death. To test the effectiveness of his machine, he arranged to abduct the Thing. The Thing's abduction was witnessed by Moon Knight who recognized Crossfire and helped the Thing defeat Crossfire's private army. Together, the Thing and Moon Knight managed to destroy the mind-control machine. Crossfire himself, however, escaped.
Despite this setback, Crossfire began work on the construction of a more advanced model of his ultrasonic brainwashing device. He arranged to have components constructed at Cross Technologies, a firm founded by his cousin, Darren Cross. Learning that the Avenger Hawkeye was employed as a security guard at CTE, Crossfire devised a plan to use Hawkeye, who he believed to be the weakest of the costumed crimefighters, as bait to lure other superhumans into trap so he could subject them to his brain-washing machine. To capture Hawkeye, Crossfire hired a trio of costumed criminals: the Silencer, Oddball, and Bombshell.
Crossfire's minions managed to take Hawkeye and his companion Mockingbird captive, and Crossfire used his ultrasonic weapon to make them fight each other. During this fight, Hawkeye suffered permanent hearing damage. However, Hawkeye eventually escaped and defeated Crossfire and his henchmen. The second machine was destroyed, and Crossfire was arrested and sentenced to prison. His subordinates were rescued by Oddball's brother Tenpin.
From prison, Crossfire discovered that Oddball and Bombshell belonged to a criminal team called the Death-Throws, a troupe of costumed criminal jugglers. Crossfire contacted and hired them to release him in exchange for a sum of money, which he would pay after being freed. Crossfire had no money at that point; his devices had been confiscated by the police, and he had lost any link to Cross Technologies.
The Death-Throws staged an attack on the prison and kidnapped the prisoner Crossfire. Once they had taken him to their HQ, they discovered that Cross had no money. They considered killing him in revenge, but they eventually decided to use the fugitive as bait to capture Hawkeye and Captain America. However, Hawkeye and Captain America defeated the Death-Throws and sent Crossfire back to prison, where he currently resides.
William Cross is a mob boss who helped Scott Lang to get money for his daughter's medical treatment. After Lang's daughter recovered, William thought Lang kept some of his money and wanted it back. Lang had to steal Hank Pym's Ant-Man suit in order to get the money, but Cross forced him to keep stealing for him using Pym's Ant-Man technology. Cross was finally defeated in battle when Heroes for Hire and Hank Pym rescued Lang and his daughter.