Lord Starkiller

Darth Stalker is an antagonist of the Force Unleashed who is actually a future incarnation of Galen Marek.

Trial of Spirit
During Starkiller's final part of his Trial of Spirit, he is attacked by the Sith Warrior who after being defeated, gives him a cryptic message that he can never escape him. He sometimes shape shifts into Cermonial Robes Galen and attacking him would hurt Starkiller.

Dark Side Ending
As Galen is turning to the good side at the end of the game, most are familiar with the ending in where he sacrifices himself and gives the rebelion new hope. But if you attack Darth Vader at the end your character will kill Darth Vader. When the Emperor tells Marek to kill his Jedi friend, he turns on the Emperor and strikes at him, but the Emperor blocks and sends Galen flying back with Sith lightning. The Emperor smashes a bypassing ship at Galen using the Force, and he ends up becoming a human-like cyborg, similar to Vader in his life-supporting suit. But in doing so turns him back to the dark side again, and again becomes a big threat, even to Sidious if he wanted more power.

Ultimate Sith
Lord Starkiller is the main playable character of Ultimate Sith Edition, he travels to Tatooine, where he kills Obi-Wan Kenobi, Jabba's Rancor and Boba Fett while in search of C-3PO and R2-D2.

He later travels to Hoth and destroys the Rebel base there, he also makes Luke Skywalker his apprentice.

He latest apperance featured him going to Endor and killing of what was left of the Rebels along with Han Solo, Chewbacca and the now Jedi Princess Leia.