Former private investigator Mac Gargan was hired by J. Jonah Jameson to find out how Peter Parker is able to get incredible pictures of Spider-Man. Gargan's efforts to locate Peter in order to find out the truth triggered Parkers's spider sense, making him easily avoidable.
Frustrated, Jameson decided to pay $10,000 to Gargan as the subject of an experiment. An experiment created by Dr. Farley Stillwell, a researcher in animal mutation which endowed the subject with the characteristic of another animal. Unfortunately the process resulted in the loss of Gargan's sanity, and the creation of the super-powered criminal menace known as the Scorpion.
Over the years Scorpion fought and was bested by Spider-Man many times. Most of these confrontations were the result of Spider-Man stepping in on an attempt on the life of Jameson, who Gargan hated even more than Spider-Man. With his mechanical tail, speed, and strength, Scorpion has always been more than a match for Spider-Man. Only the skill, experience, and quick wit of the web head helped him defeat Gargan.
Later on, Scorpion was recruited by Norman Osborn, informed of Spider-man's real identity, and ordered to kidnap Peter's Aunt May if anything should happen to Osborn. In the middle of his task Scorpion was approached by the recently freed symbiote. Risking Osborn's wrath, Gargan chose the symbiote over Osborn's mission, since the symbiote's potential for power was far greater than any newly designed Scorpion suit could ever be. Thus transforming Scorpion into the even more monstrous Venom.
I got permission to fan edit, so please check out his gallery!