Confederacy of Independent Systems
The Confederacy of Independent Systems was an organization of planets that attempted to secede from the Galactic Republic. Lead primarily by large corporate conglomerates, they fought a civil war against the Republic that began with the Battle of Geonosis.
The number of star systems under their control was estimated in the tens of thousands. Count Dooku was successful in luring corporate-run armies by promising unregulated capitalism as opposed to the unpopular taxes the Republic had imposed.
The destruction of the CIS was completed by Anakin Skywalker in one of his first acts as Darth Vader. He travelled to Mustafar, where he assassinated the CIS' leadership and sent the shut-down signals to the quadrillions upon quadrillions of battle droids scattered throughout the galaxy, as well as to the automated factories producing the droids.