Requirements:

DB Gloves
Perk: Assassins Blade
High Sneak
2 Dwarven or better daggers,

And finally an unsuspecting DRAGON!

Sneak up on him and then, equip DB gloves for double the backstabbing damage, which with te perk assassins blade is 15x will make it into a whopping 30x multipier!!!!

Power attack it with your dual daggers and enjoy the dragon soul