Level 44, Deadly Dragons, Wars in Skyrim, Shout Cooldowns reduced by 75%, Thuu'mic voice activated shouts, my two legendary daggers only hit for 90, Only high resistance was frost, and not even invisible will allow me to get stealth on this dragon, I use health potions under a self imposed 'overdose' system where I refuse to utilize more then I feel healthy to my character and won't mix multiple buff effects due to my 'complications' theory that it would be bad for you to mix the active ingredients of opposite alchemical mixtures.
I fought a Wyrm, this thing was nigh immune to damage, took me over an hour of reloading to finally get a successful victory by timing out the Feim (Become Ethereal) shout to block his instant kill breath attacks and take preemptive melee hits, hiding in towers to drop aggro, and using the sprinting critical strike for double damage. My single successful stealth power attack
(Base damage+Dual Savagery+Standing Power Attacks x Assassin x hits in the dual power attack)
(90+50%+25%x15x3=7593.75 Damage)
Dealt only 20% of this dragons health bar, I could NOT for the life of me get a second stealth crit and had to fight this things remaining 30,000 effective health (Hp multiplied by damage resistance such as armor) in fair combat with the max damage I could achieve being a few hundred points at a time when everything it did was capable of instantly killing me except its ice magic.