Mr. Li, aka Negative Man, cured Eddie Brock of his cancer and Venom symbiote. However, the Venom Symbiote found Brock again, but upon bonding with him, the Symbiote was repelled due to Negative Man's powers and it formed the Anti-Venom symbiotie
Anti-Venon, inspired by Spider-Man's heroism, decided to help Spider-Man against Venom, bonded to Mac Gargan. Anti-Venom was forced to use his powers to rid Spider-Man of the Venom symbiote, in turn almost ridding Spider-Man of his powers completely.
Anti-Venom became an ally to Spider-Man, and helped him with Oscorp. Anti-Venom faced Gargan, who was without his symbiote. Gargan poisoned Anti-Venom, seemlingly destroying his symbiote. Gargan was about to kill Eddie Brock, but the Venom Symbiote wouldn't let him, because the Venom symbiote loved Eddie Brock too much. After this, Anti-Venom became a regular hero.