Star Wars: The Force Unleashed II picks up six months after the end of Star Wars: The Force Unleashed. Starkiller, Darth Vader's secret apprentice, was killed by Darth Sidious after betraying his former masters and joining with the enemy. Or so it seemed. Force Unleashed 2 begins with Vader walking into a large room with a prison cell in the middle. In it, is none other than Starkiller himself. Suffering from visions of a woman's voice and a burning forest, Vader tells him that those are memories of a dead man, and that he is actually a clone of the original Starkiller. Vader gives him a test to strike down a few training droids and Starkiller abides, but when asked to take out one that looks like Juno Eclipse, his love interest in part one, he couldn't do it. Being told that he failed just like the rest of the clones, Starkiller unleashes a powerful force lightning attack and escapes. The clone then sets off on a mission, to not only discover the truth about whether if he is a clone, but to also find the whereabouts of Juno Eclipse.

In the game, the player controls Starkiller in his quest to get the answers he wants. This will take him to a number of famous planets in the Star Wars universe including Kamino, the watery world home to the cloning facility; and Dagobah, the swamp infested planet housing one particular exiled Jedi. Starkiller is equipped this time with powerful dual lightsabers. An improvement to the game allows Starkiller to actually dismember his enemies with his lightsaber, which can result in stormtroopers with no arms or even no head. All force powers from part one return with a new upgrade mechanic to go along. Using Experience Points gained from killed enemies, the player can upgrade any force power up to the maximum of 3 levels. This includes the new force power known as Mind Trick, which Starkiller can use to take over the mind of the Empire's forces and make them do things such as attack their own allies or even commit suicide by jumping off buildings.

Holocrons return in this sequel and are scattered throughout each level. Finding one can lead to an upgrade in health or force energy, new lightsaber colors/powers, or even a new costume to equip you with. There is also a Challenge mode where the player can participate in a series of 10 challenges ranging from time trials to gauntlet trials (fighting waves of enemies). The faster you do the challenges, the higher of a score you will get; with the lowest being a Bronze medal and the highest being a Platinum medal. Doing the challenges also help to get new achievements/trophies.