Right now, the Blade of Woe and a Legendary Ebony dagger, but with the amount of damage a power attack using both does (around 140 if I recall correctly), my perk that makes sneak attacks with daggers do 15x damage, and my "Shrouded hand coverings" that make sneak attacks with daggers do another 2x damage, I end up with 140 x 30 which comes out to 4200.