The Apprentice (Starkiller) can be difficult to beat. So you might need a good strategy to take him on in Soul Calibur 4.
If you’re trying to unlock The Apprentice, you will need to use Vader in Arcade mode and beat him. A good strategy is to assign R2 the A+G button combo. This gives Vader the Emperor Toss move as a grab. The Apprentice seems to be very vulnerable to this move. Do it over and over again and you will be able to defeat him.
See also: How to unlock all 18 Soul Calibur 4 secret characters and treasure chest items (guide)
