Start a new game (have it be master difficulty)
At the very beginning of the game choose imperial.
When you get to the tortune chamber pick up the knife on the table with the knapsack and book.
Wait for hadvar and the assistant to leave.
Sneak behind the torturer until you are hidden and keep hitting him (power or normal, doesn't matter) with the dagger.
Your sneak levels so fast and easy and since his health recovers he can sure take a beating. He also won't attack you if you stay hidden. He may walk a little bit but thats only becuase you pushed him out of position.