There are different endings in Star Wars: The Force Unleashed, depending on whether you choose the dark side of The Force, or the path of redemption. Some sources speculate that there are multiple endings, including endings that break off from the Star Wars "canon," while other sources hold that there are only two endings in the game. This page contains spoilers and information about the Star Wars: The Force Unleashed story and endings.Nintendo.com: [Star Wars: The Force Unleashed game details pageIGN: Star Wars: The Force Unleashed Wii Preview (August 17, 2008)

1. Publisher: LucasArts
2. Platforms: Xbox 360, PS3, PS2, PSP, DS, Wii, iPhone, N-Gage
3. Genre: Action
4. Mode: Single player
5. Release date: September 16, 2008

Do not read further about the Star Wars: The Force Unleashed endings if you don't want the story spoiled. Towards the end of the game, the Emperor commands you to finish off Darth Vader. This is the “dark side” ending, in which you will do battle with Darth Vader and eventually kill him. Upon beating Vader, Starkiller then approaches the Emperor, who has General Kota subdued. Sure to be the Emperor's new pawn, Starkiller is ordered to strike down Kota. Starkiller then attempts a coup, striking the Emperor instead, who deflects the strike, and then uses The Force to bring down a space ship on Starkiller. When Starkiller awakens, he is being operated on by robots, and has mechanized arms, similar to Darth Vader himself at the end of Revenge of the Sith. In essence, Starkiller replaces Darth Vader and goes on to do the Emperor's bidding.GameFAQs: The Dark Side ending (SPOILERS!)

At a certain point in the game, Starkiller defeats Shaak Ti, the Jedi High Council member. Upon returning to Darth Vader, the Emperor discovers the identity of Starkiller—previously unknown—and orders Vader to destroy Starkiller. Vader complies, though he eventually saves Starkiller and keeps him secret. After this event, Vader has Starkiller help organize the Rebel Alliance. This is a big revelation, since it means that Darth Vader in part orchestrated the events leading to the Emperor's downfall and his own death in Return of the Jedi. After certain key members of the Rebel Alliance are captured and imprisoned in the Death Star, Starkiller breaks them out, but is himself captured by the Emperor. The Emperor forces Vader and Starkiller to duel, and when Vader fails, the Emperor kills Starkiller himself. This Light Side ending ends with Starkiller sacrificing himself for the Rebel Alliance. The Alliance's sybmol is taken from Starkiller's—whose true name is Galen Marek—family crest.IGN: Rumored ending to The Force Unleashed

1. Wookiepedia says "several" endingsWookieepedia: Star Wars: The Force Unleashed Gameplay Info
2. IGN says "two endings"IGN: Star Wars: The Force Unleashed Wii Preview (August 17, 2008)
3. The game's demo featured different ending from the full gameVideoGamer.com: Star Wars: The Force Unleashed demo next month (July 28, 2008)
4. Nintendo.com says "multiple" endingsNintendo.com: Star Wars: The Force Unleashed game details page
5. Haden Blackman, project leader for The Force Unleashed, commenting on the endings: I hope [players] like them... I think that the endings are true to the spirit of the story, and really show the consequences of your choices, even if they don't all fit perfectly into canon.—Haden BlackmanXbox360Achievements.org: Star Wars: The Force Unleashed Interview (July 25, 2008)