If you focus on sneak, then you can get sneak attack X15 with daggers upgrade. I then got X2 sneak attack from Dark Brotherhood gloves and I then had a grand total of X30 MULTIPLIER!!!!
This ONE hits a mammoth, giant and pretty much everything I've come across, Bosses included.
This is using dual wield daggers.

yeah melee of any kind really stomps in this game, and scales a bit too high imo.

I'm doing the same. I can one hit basically everything and I'm only level 20.

Yeah, I am doing well with just x15. I def want x30. Can you get x2 without joining the Dark Brotherhood? I am a sneaky female Orc knife fighter with sneak 100 but I dont want to be an assassin. Is there a way to get x2 elsewhere? Or a Dark Brotherhood membet I can murder and loot to get it?

Not sure, but you get the gloves more or less straight away when you join. You don't have to do much assassinating
I have loved the DB missions and by completing the Dark Brotherhood you get LOADS of money! and some excellent sneak armour.