Operation: EndGame

Operation: EndGame was the name of Dr. Ivo Robotnik's final plan to wipe out Knothole and dispose of the Knothole Freedom Fighters, specifically Sonic the Hedgehog, once and for all. The plan had numerous phases and was nearly carried out to completion, but due to Snively betraying his uncle, the plan fell apart when the Ultimate Annihilator targeted only Robotnik, erasing him from existence.

Prelude
When Sonic used Dr. Quack's invention - the Dream Watcher - in order to enter King Max's psyche to contact him during his coma, Robotnik managed to track the location of Knothole when he detected the Neutron Chip in Quack's device. While Sonic and the Freedom Fighters were absent from Knothole retrieving the Sword of Acorns, Robotnik sent Snively and a group of SWATbots to apprehend Dr. Quack and King Max, with the latter being replaced by a robotic duplicate. Fearing Sonic would interfere with his plans, Robotnik appealed to former Wolf Pack member Drago Wolf to set up Sonic as a criminal for Sally Acorn's death. Dr. Quack originally refused to work for Robotnik in helping assemble the Ultimate Annihilator, but when Snively brought Dr. Quack's wife and kids and threatened to roboticize them, he complied. (StH: #43, #50, SSS: #1)

Phase One
The first phase of Operation: EndGame was to have Princess Sally Acorn killed while framing Sonic for her murder. Drago managed to convince Hershey Cat to wear a suit that made her look like Sonic, while the suit's eyes made it so anyone Hershey saw while wearing the suit looked like Snively. During one of their missions in Robotropolis, Sally ended up hanging on to a rope high above the ground. Hershey, believing it to be Snively, cut the rope, causing Sally to fall to what appeared to be her death. With everyone witnessing what they believed was Sonic killing Sally, the Freedom Fighters targeted Sonic as a fugitive. (StH: #47, #49)

Phase Two
Robotnik used the robotic duplicate of King Max to order the Royal Secret Service to track down and apprehend Sonic. While Knothole's main defence was absent, Robotnik's army of SWATbots invaded the village, holding its citizens prisoners. (StH: #48, #49)

Phase Three
Originally, Robotnik planned to fire the Ultimate Annihilator and wipe out the hostages in Knothole. However, when Dulcy informed the Secret Service and Knuckles the Echidna of Sonic's innocence with regards to Sally's murder, the group liberated Knothole before Robotnik could fire the weapon. Despite this, Robotnik planned to erase Knothole while Sonic went to Robotropolis to avenge Sally's death. Although Robotnik managed to activate his weapon, he was unaware Snively had reprogrammed the weapon to only target only him. After a brief fist fight with Sonic, the Ultimate Annihilator fired, erasing Robotnik from existence. (StH: #50)

Background Information
The arc which Operation: EndGame was carried out was also called "End Game".