Kasady is a psychopath and a homicidal sadist. He is a deeply disturbed individual with a dark past: as a child, he killed his grandmother by pushing her down a flight of stairs, tried to murder his mother by throwing a hair dryer into her bathtub, and tortured and killed his mother's dog, with a drill. After the latter, his mother then tried to kill Kasady, and was apparently beaten to the brink of death by Kasady's father, who received no defense from Kasady during the trial. As an orphan, Kasady was sent to the St. Estes Home for Boys, where his antisocial behavior made him the target of abuse from both the other orphans and the staff. Kasady gained revenge by murdering the disciplinarian administrator, pushing a girl (who laughed at him for asking to date her) in front of a moving bus, and burning down the orphanage. It was during his brutal years at St. Estes that Kasady acquired his philosophy that life was essentially meaningless and futile, that "laws are only words",[12] and came to see the spreading of chaos through random, unpattern bloodshed as the ultimate freedom

Kasady became a serial killer. He was then captured and sent to Ryker's Island prison for 11 murders though he bragged about killing a dozen more,where he shared a cell with Eddie Brock, the host of the alien symbiote that turns into the supervillain Venom. When Brock's symbiote soon returned to be bonded again, allowing Venom to escape prison, the symbiote unknowingly left its offspring in the cell. due to its alien mindset, the symbiote felt no emotional attachment to its offspring, regarding it as insignificant, and thus never communicated its existence to Brock via their telepathic link. The new symbiote then bonded with Kasady, transforming him into Carnage


The bond between the Carnage symbiote and Kasady was stronger than the bond between Brock and the Venom symbiote. As a result, Carnage is far more violent, powerful, and deadly than Venom.He escaped prison,and began a series of murders, and at the scene of each crime, wrote "Carnage" on the walls with his own blood. He was found by Spider-Man, though the hero proved to be no match for Carnage's powers. In desperation, Spider-Man made a truce with Venom to fight Carnage.The Carnage symbiote was defeated and apparently destroyed with sonic weaponry. But Carnage would Return, and he always finds a way, to spread more carnage