I'm using the statistics for Daedric Weapons in Oblivion as the base number, and those are:
Daggers: 19
Shortsword: 21
Longsword: 24
Claymore: 26
Mace: 24
War Axe: 22
Battle Axe: 26
Bow: 21
Arrow: 15
For enchanting, we will assume an elemental effect for an additional 10 Base dmg.
And for a poison, we will also work with 10 dmg, for simplicity's sake.
Here we Go.
Dagger: 19dmg
Sm Daedric Smithing for improved blade by double: 38dmg
1H Armsman (5 of 5) for 100% more damage: 76dmg
Sn Assassin's Blade for 15x damage: 1,140dmg
1,140dmg+
Fire Enchantment: 10dmg
En Extra Effects for another +10dmg : 20dmg
En Enchanter (5 of 5) for 100% stronger enchant : 40dmg
En Fire Enchanter for 25% dmg : 50dmg
50dmg +
Poison of Damage Health: +10dmg:
Al Alchemist (5 of 5) for 100% stronger poison: 20dmg
Al Purity (no positive effect): 20dmg
Al Poisoner for 25% stronger poison: 25dmg
1,140
+
50
+
25
----
1,215dmg in one hit.
If i left out any possible multipliers, let me know. Post below if you think you can find a way to beat this attack using these figures (which are not perfect, but as long as we agree to use them, the results will be fair).
Cheers.

