The Ultimate Annihilator was a devastating satellite weapon created by Dr. Ivo Robotnik in 3235 capable of erasing matter. Although he began creating a prototype during the Great War, its early development was ended when he was sentenced to ten years in prison for wanting to test the weapon on live Overlanders. (StH: #50, #72, SSS: #6)

Robotnik had intended on using the device to erase Knothole from existence and thereby defeat the Freedom Fighters once and for all. The weapon was powered by irradiated ore and first tested on an Overlander captured from Mega Central. (SSS: #4, #6)

Although Robotnik managed to fire the weapon and hit Knothole, his nephew Snively had altered its programming beforehand to not only spare the village (it was instead trapped inside a pocket dimension 3 hours ahead of its original timezone), but to specifically target Robotnik's DNA. Thus, only Robotnik was erased from existence. Furthermore, the weapon being fired had after effects, including weakening the dimensional barriers with other zones and returning Echidnaopolis to Mobius Prime, as well as allowing the Dark Legion to escape the Twilight Zone. It also restored the free will of the roboticized Mobians (StH: #50, #75, KtE: #1, #5)