First make sure that you have a Destruction skill of 100 or higher and go to the Arcane University.
In the Arcane University, go to the Altar of Spellmaking and make a spell that does Damage Health 100 pts. for 1 sec, Weakness to Magicka 100% for 1 sec, Weakness to Fire 100% for 1 sec, Weakness to Frost 100% for 1 sec, Weakness to Shock 100% for 1 sec, Fire Damage 100 pts. for 1 sec, Frost Damage 100 pts. for 1 sec, and Shock Damage 100 pts. for 1 sec.
This will cause at least 1000 pts. of damage all in one spell.