Believe it or not, Norman Osborn actually wasn't the first Goblin. Some years before he went green with evil, Osborn tested what would come to be known as the "goblin serum" on one of his employees.
That employee, Nels Van Adder, doesn't do too well with the serum (well, neither did
Norman, but that's another story). The serum transforms Van Adder into a hulking, red-skinned monster, which starts killing people in a mindless rage. Before Van Adder can kill Norman, the beast is knocked out of a window by the timely arrival of Captain George Stacy and his brother Arthur. The Proto-Goblin fled the scene after that, and has never been seen since, so technically, Van Adder has never actually encountered Spider-Man — yet. But he is a Goblin.
You'd think this experiment gone awry would've been enough to put a stop to Norman's plotting, but unfortunately, the Goblin saga had just begun.