Throughout the Clone Wars, the Separatist Alliance relied almost exclusively on droids to fill its ranks.
While most battle droids were inferior to their clone counterparts, being produced quickly and cheaply in large numbers, some were far more competent, using the best weapons and technology available to make them as lethal as possible.
5. Buzz Droid
While most Separatist starfighters were poor compared to their Republic opponents, they had other weapons at their disposal, including ones that even Jedi weren’t safe from. Buzz droids were carried inside missiles that detonated close to enemy fighters, sending dozens of the droids to attach onto the ship and start cutting it apart.
While they weren’t powerful enough to destroy a ship entirely, they could still breach sealed cockpits or attack astromechs, disabling the craft. Buzz droids were a difficult threat to combat, too. Skilled pilots could shoot them off each other’s fighters, or they could be shaken off, but it had to be done quickly before they destroyed the ship’s vital systems.
4. BX-series Commando Droid
Though they shared some design similarities with their B1 counterparts, the BX-series was much more advanced, designed for carrying out complex missions. They were among the most lethal droids deployed by the CIS; fast, agile, and adaptive, they carried a range of weapons, including vibroswords for melee combat.
The commando droid’s biggest feature was its increased intelligence. They were able to carry out complex stealth missions and infiltration, even disguising themselves in clone armor to avoid detection, and didn’t display the programming glitches of regular droids.
3. Droideka
Although it was an old design, dating to before the Invasion of Naboo, the droideka was still a formidable weapon by the time of the Clone Wars. Designed solely for combat and armed with twin blasters and energy shield, the droideka could roll quickly about the battlefield before unfolding and laying down a deadly suppressive fire.
The droideka’s biggest weakness was in its shield, which allowed slow moving objects to pass through it. Republic troops used special tactics to exploit this, rolling grenades slowly through the shield, a move that required perfect timing to execute effectively.
2. IG-100
A rare machine in the Separatist military, the IG-100 was primarily used as a bodyguard, protecting important commanders like Dooku and Grievous. Capable with most weapons, they usually carried electrostaffs as a defense against lightsabers, and were able to take on a Jedi when in groups of two or three.
Their advanced artificial intelligence made them more versatile, and they were able to expertly pilot starfighters. They could also learn from experience, with Grievous personally training his bodyguards to fight against lightsaber wielders.
1. ST-series Super Tactical Droid
With most of their soldiers being droids, it made sense for the CIS military to use them as commanders too. Even human and alien officers often had a tactical droid to advise them in battle. The most advanced model was the ST-series which was used to command large ground battles and fleet actions. They could calculate their opponent’s strategies to fine degrees, working out the odds for every possibility.
ST-series droids also had a certain amount of independence. They could operate alone and developed individual personalities, taking names and customizing their armor. One droid, named Kalani, even refused the order to shut down all Separatist military units at the end of the war, believing it was a trap, and spent over a decade stranded on Agamar, waiting to rejoin the war.