Eddie Brock, the original Venom, first came in contact with the symbiote when he was praying for forgiveness for the sin of suicide. Diognosed with terminal adrenal cancer and having lost his job and wife, Edward "Eddie" Brock attempted to take his life only to find a new one as the being known as Venom when the symbiote rejected by Spider-Man bonded with the ex-journalist. After years of being a super-villain/anti-hero, and trying to kill Spider-Man, Eddie's cancer finally caught up with him and he sold the symbiote for two million dollars, was found not guilty of his crimes while bonded with his "other", and started working in a soup kitchen run by Mr. Negative (granted while having no idea who his real employeer was). As Eddie was doing what he thought was good, he was being cured of his cancer through Mr. Negative's powers. Eventually completely cured of his illness Eddie thought he would live out his life as a humble man working behind the scenes for others, but when Spider-Man and current Venom (Mac Gargon) crashed through the soup kitchen he was at things changed. The symbiote tried to bond with Eddie again, but found that it couldn't as the latent cells inside Eddie's body left behind from the years of being bound to the symbiote now had mutated and were caustic to Venom. Although still very skinny from just being over cancer, the combination of mutated symbiote cells and Eddies own lymph system created a new symbiote Anti-Venom. In the insuing fight Anti-Venom nearly destroyed the Venom symbiote, attempted to cure Spider-Man of the residual Venom cells in the wall crawler's body, and was thought killed by the poison of Mac Gargon's Scorpion costume. After leaving the soup kitchen, curing a drug addict, and taking out a drug cartell with Punisher, Eddie was last seen driving through the Mexican badlands in a jeep with his newest love interest to parts unknown.
Unique in symbiotes, Anti-Venom's costume does not seem to have an intelligence of its own, but is only an extension of Eddie's own body. Also no weakness to fire or sound has been shown and the need for chocolate and/or brains is not seen in this symbiote. Anti-Venom also has all of Venom's powers and more. Able to lift over 100 tons, heal from any damage (including having his brains blown out with a shotgun at point-blank range), treat any disease and poison in his and other's bodies, and manipulate his symbiote covered body to grow more bulky or skinier, change from a friendlier form to a more frightening one, and with complete immunity to fire, Anti-Venom is a very different version of Eddie Brock than he was as Venom. Important to note is that he has given up on his hatred of Spider-Man and is now focused on stopping Venom once and for all.