After Stan Lee and Steve Ditko brought Spider-Man into the world in Amazing Fantasy #15, they gave the web-slinger his first supervillain in The Amazing Spider-Man #1. Before the Vulture, Doctor Octopus and Sandman menaced Peter Parker, Dmitri Smerdyakov, the Chameleon, was Spider-Man's first real villain. As the master of disguise and half-brother of Kraven the Hunter, the Chameleon is a master of subterfuge and misdirection, and he's able to disguise and impersonate anyone he desires. Despite all that, it's easy to write him off as one of the less intimidating villains in a rogues' gallery that's filled with symbiotes and goblins.
But in the early 1990s, the Chameleon pulled one of the cruelest, most sadistic plots that Spider-Man has ever faced. By playing to his strengths of deception, the Chameleon tricked Peter Parker into thinking his parents came back to life.
THE RICHARD AND MARY PARKER PLOT
The mastermind behind bringing Peter Parker's parents to life was not Dmitri, but rather Harry Osborn. While Harry ultimately would not live to see the plan reach its conclusion, Harry Osborn concocted the whole plot as one huge practical joke on Spider-Man to emotionally break him. However, there was no one better to enact his scheme than Chameleon, who had access to technology that would perfectly duplicate Parker's parents.
It didn't take much to convince the Chameleon to create the Life Model Decoys. At that point, Dmitri's half-brother, Sergei Kravinoff, had committed suicide after "conquering" Spider-Man in the epic story Kraven's Last Hunt. The Chameleon held Spider-Man entirely responsible for his half-brother's demise and vowed revenge on the wall-crawler.
While Chameleon didn't know Peter Parker was Spider-Man, he did know Peter as the photographer who took Spider-Man's photos for The Daily Bugle. Therefore, Osborn convinced Chameleon that, by bringing Peter's parents back from the dead, they might be able to convince Peter to tell them Spider-Man's secret identity. Of course, Osborn already knew Peter was Spidey, but the Chameleon didn't.
RICHARD AND MARY'S RETURN
Right after Spider-Man finished up his first major encounter with Carnage, Richard and Mary Parker seemingly returned from the grave in The Amazing Spider-Man #363, by David Michelinie and Mark Bagley. In reality, these two were Life Model Decoys that were completely under the Chameleon's control. Although they stated that they had been trapped elsewhere in some prison plant, the Chameleon used this moment to monitor Parker.
During the years over which this plot took place, Peter's parents proved to be a new point of vulnerability. Venom even kidnapped them at one point in an attempt to protect Peter's innocent parents from Spider-Man's toxic influence. Ironically, Harry Osborn died in an act of redemption during this entire plot, letting go of his grudge against Peter. Still, Chameleon, despite his partner-in-crime's death, continued with the plan anyway.
All the while, Aunt May remained suspicious about the Parkers since they didn't seem to know key details from the past. However, Peter remained optimistic that his parents had indeed returned. It didn't help that, between Harry dying and the Maximum Carnage event, that Peter's parents offered him a respite from the pain in his life.
This all culminated in Michelinie and Bagley Amazing Spider-Man #388-389, where Peter learns the truth about his parents after revealing his secret identity to them. They darted off to the Chameleon to report their finding, with Peter tracking them down. Before they could reveal Peter's secret to the Chameleon, however, Peter interrupted the proceedings, learning the horrible truth in one instant. Chameleon ordered Peter's parents to kill him, but his mom, entangled by some maternal instinct for her son, stopped "Peter's father" from killing him after morphing into a new, more robotic form.
While Spider-Man ended up beating Chameleon down and learning the truth, this incident left Peter utterly devastated. He had to suffer the loss of his parents all over again, which left him heartbroken and beaten at the hands of his first super-villain adversary. Although the Chameleon has attacked Spider-Man on numerous subsequent occasions since then and is currently planning something new in Amazing Spider-Man, he's never reached the cruel heights of this event and its years-long deception.