As a child, Edward Whelan was regularly molested by his father; a wealthy and influential judge. As a protective measure, Edward would shut himself down and suppress these memories, burying deep and festering feelings of hatred, rage, shame, and loathing for his father and for himself. They lay dormant into Edward's adult years, when he became a successful geneticist.
Major Story Arcs
While searching for Arnim Zola, Edward found himself in the employ of Baron Zemo, only to discover that Zemo had been transforming human beings into hideously deformed mutates. When Edward objected, he found himself becoming Zemo's newest test subject, undergoing torture and experiments which unleashed the hidden ugliness within. The years of abuse left Edward feeling so low and ashamed that he was virtually sub-human, a worthless thing, nothing more than vermin. Transformed into a rat-like creature, Vermin's intelligence was that of angry child, and he loyally served Zemo until they were both defeated by Captain America.
The Sewers of New York
Fleeing into the sewers of New York City, Vermin reemerged with an army of rats at his command, but was again defeated by Captain America with the help of Spider-Man, who inadvertently triggered lifelong and severe arachnophobia within Vermin. Escaping to the sewers, Vermin cowered from Spider-Man, emerging only at night to murder and cannibalize innocent citizens. He found himself targeted by Kraven the Hunter, in disguise as Spider-Man, who defeated Vermin and held him captive as bait for the true Spider-Man, who was in a severely weakened state. Vermin defeated and nearly killed the hero, but was stopped by Kraven who released Vermin back to the sewers as a distraction for Spider-Man while Kraven committed suicide. Spider-Man defeated Vermin by tricking him to flee outside during the daytime, which confused and terrified the man-rat, whom Spider-Man then left in the care of Reed Richards.
Discovering that Vermin's mutation was more rooted in psychology than biology, Richards handed Vermin over to the care of Dr. Ashley Kafka at Ravencroft Sanitarium, the first person who was able to get through Vermin and reach the Edward Whelan within. After feeling abandoned and betrayed when Dr. Kafka took a day off, Vermin flew into a rage, killing several guards and cops in his escape. After encountering a hallucination of himself as a little boy, he took the "child" under his protection, and sought out their home to kill his/their father. He nearly succeeded, but the love he still had for his father kept him from acting on his hatred, and he tried to commit suicide by provoking the police outside to open fire. He was saved by Spider-Man, and returned to the care of Dr. Kafka, where he became more violent and desperate between transformations back to his original human state. He knew he was dying, and like a scared rat in a corner, that made him even more dangerous.
Vermin was one of the many villains given the choice to join the Thunderbolts army or go to jail. Vermin chose to join the Thunderbolts, but has since been returned to custody.
Kraven set up a big game hunt with rich donors to target New York's animal themed villains for disrespecting the animal kingdom. With Arcade, Kraven specifically targeted Vermin and experimented on him to create multiple clones. They were to be used to help corral some of the villains and be treated as cannon fodder, however, they were able to escape into the sewer system.
Vermin has enhanced strength, able to lift up to 1,000 pounds. He has enhanced speed, enabling him to run at approximately 35 miles an hour. His senses are super-humanly keen, especially his sense of smell. His stamina, durability, reflexes and agility are all also beyond normal human levels. Vermin also have the power to control stray rats and dogs within a two mile radius. Vermin uses a feral fighting style so unpredictable that even experienced fighters like Captain America and Spider-Man have no way of knowing the creature's next move.
Vermin is a villain in the 2012 The Amazing Spider-Man Game. In the game, an Oscorp geneticist named Edward Whelan is accidentally transformed into the beast that is Vermin. He becomes the main source of infection in New York and battles Spider-Man. He even infects Gwen Stacy by biting her.