Venom is a Symbiote created from Spider-Man's DNA by Doctor Octopus for Oscorp. This living organism that can attach itself to a human host to form an almost unstoppable villain. He is the tertiary antagonist of Season 1 and a minor antagonist in Season 2. He is also another one of Spider-Man's arch-enemies.
Venom is a symbiote created by Dr. Otto Octavius after obtaining from a blood sample from Spider-Man left in a battle with an Octobot. At the same moment it was created, the 'living suit of armor' started to act aggressively as it was made from all the deadliest aspects of Spider-Man's DNA. Despite Octavius needing few months to perfect the life-form, Norman Osborn only gave a month to do so. After Otto tells Osborn about needing more time to have something for that night, the symbiote escaped and wanted to return to where it came from: Spider-Man. The organism followed Peter Parker to Harry Osborn's party. After realizing that Peter is Spider-Man, it became confused and began jumping from host to host. Using its ability to latch onto anyone, it latched onto Flash Thompson, Nova, Power Man and Iron Fist in the process. After finally bonding to Spider-Man, it became complete and proclaimed itself as "Venom" and attempted to kill Spider-Man's allies. When the symbiote targeted Harry and Mary Jane Watson, Spider-Man suddenly began to regain control and fight back, and eventually broke free. Although the organism bested its host in hand-to-hand combat, Spider-Man trapped and shocked the symbiote with his "electro webs", seemingly destroying the symbiote. Unknown to most people, a small piece of the symbiote ended up on a piano in the Osborn family room at some point. Without Peter noticing, Harry scraped it into a bottle, trapping and keeping it.