Wait
WHAT? HOW?
100 enchanting, all perks.
Enchant armor, gauntlets, necklace, and ring with fortify smithing.
Improve an ebony one/twohander to legendary while wearing all of them.
Next, improve gauntlets, boots, necklace, and ring and anything else you can with fortify one/twohanded.
By this point, an ebony sword does about 250 damage per hit.
A power attack will kill any dragon in one hit.