Recognizing the value of teamwork, the Beetle (now MACH-IV) gathered together a group of super-villains (Boomerang, Speed Demon, Rhino, and Hydro-Man) and created a loosely-organized team known as the Sinister Syndicate. Knowing their reputation was on the line, they sought to band together in hopes of banking in on their combined power. They were first hired to stop Spider-Man and Silver Sable from apprehending the terrorist Jack O'Lantern, and they nearly succeeded, too, if were not for the arrival of Sandman, who had then decided to renounce his criminal ways and helped the heroes.
They returned under the Beetle’s urging once more, but this time their desire was primarily revenge on their common enemy, Spider-Man. During this time, the Syndicate inducted the Shocker among their number, as well as Leila Davis. The Syndicate was hired to kill a scientist who owed a large gambling debt, and the Beetle dealt the killing blow. Unfortunately, the members of the Syndicate succumbed to the grudges they held among each other, compounded by the fact that the crime lord Kingpin was manipulating events as part of his own, unrelated scheme. Despite their bickering, these “Deadly Foes of Spider-Man” actually succeeded in felling the wall-crawler, but the Rhino refused to be a party to murder, instead hoping to just rob enough money to remove his armored suit, and the team abandoned Spider-Man.
Later, Leila Davis revealed herself to be the widow of the Ringer, and she held the Beetle responsible for his death at the hands of the Scourge of the Underworld. Lelia struck with the Ringer’s weapons during a battle with Spider-Man, and the group was torn apart by in-fighting and easily captured.