Since Ahsoka Tano vs Starkiller isn't fair, I decided to throw Anakin in the mix.
Anakin is about as powerful as he was during the Clone Wars series (his prime) and Ahsoka is at her best.
Starkiller is at his best (his prime, A.K.A the first game). This is a random encounter on Coruscant.
Explain your reasoning. Say why you think one character would beat another.