Annihilation

An explosion of power, you annihilate a creature with a snap. Roll a spell attack with disadvantage. if you hit, roll all dice you have, total it up, and divide by 2. Target takes this damage. If you miss this spell attack, take 2d20 psychic damage, and expend 1 of each level spell slot.

This spell ignores resistances, and expends all spell slots for a week.