Sparred with Starkiller for hours

He fought like a machine, too, with relentless blows and single- minded aggression. The first time they had dueled, in Starkiller's first life, Vader had displayed no anger at all-just determination, not to kill his apprentice, but to wear him into submission. The fight had raged across the training deck of the Executor for hours, with Starkiller never landing a single blow, no matter how he tried. He had gone from excitement at thinking that he had graduated to a new level of mastery to realizing just how much he had left to learn. More fuel had been added to the hatred he had felt for his Master and tormentor, along with a twisted kind of love for the man who made him stronger by showing him how weak he was. The fight had only stopped when Starkiller collapsed unconscious from exhaustion and was dragged by PROXY to his meditation chamber.


The Force Unleashed 2, Chapter 15, Page 273