Unerring Strike

You point your finger at a creature in range and grant it the ability to gain insight into an enemies defenses. On the creature’s next turn, it can make it's first attack with Advantage, and it deals extra damage of the same type equal to the difference between its attack roll and the targets AC. Provided that the triggering attack hits, and this spell hasn't ended.

The extra damage increases by (1d6) when you reach 5th level, (2d6) at 11th level, and (3d6) at 17th level.