The Spider-Slayer was a robot built by scientist Henry Smythe, a supporter of J. Jonah Jameson's anti-Spider-Man editorials, and created to apprehend the webslinger. Overjoyed at the idea of being the one to capture the vigilante by means of this powerful robot, Jameson operated it by remote control and chased Spider-Man all over New York City by virtue of its ability to follow Spider-Man anywhere thanks to tracking his "impulses," being able to climb as easily as he did and being impervious to his webs. Eventually the Spider-Slayer seized him atop a skyscraper, but while Jameson and Smythe were traveling there by taxi to collect their prey, Spider-Man managed to pry open a panel on the robot's chest and rip out its wiring. When the two conspirators arrived, they only found an empty costume stuffed with webbing.
The robot was never specifically referred to as the Spider-Slayer during the episode, although it is obviously based on the comic storyline.