Anti-troopers were the last line of clone troopers based on the genetic template of Jango Fett created by the Kaminoans who were activated to free their home planet of Imperial occupation. Originally trained to be clone jet troopers, anti-troopers utilized jetpacks, granting them the advantage of height and speed in combat.
Discovering the rogue clone army in 12 BBY, Imperial high command send the 501st Legion to destroy the uprising and the regain control of Kaminoan. Lead by the bounty hunter Boba Fett, an unaltered clone and 'son' of Jango, the 501st attacked the Kaminoan capital of Tipoca City. Though they met fierce resistance from the anti-troopers and a supplementary force of Rail-class Advanced Recon Commandos, they were ultimately successful and the uprising was crushed.
The creation of the anti-troopers caused a reformation of the Imperial military. Clone troopers based on a single genetic template were replaced by a wider variety of genetic templates until clones were phased out entirely by birth born humans. Though several clones did still continue to serve in the Imperial military.
Battle vs. EXALT (by Monkey Doctor 33)