Curse of Weakened Armor

You place a curse on a creature (that is wearing armor or has natural armor) that you can see within range. Until the spell ends the target has their AC lowered by 1. In addition the target  takes 1d4 extra force damage whenever it is hit. When the target drops to 0 hit points before this spell ends you can use a bonus action on your next turn to place the curse on another creature. The spell ends early if remove curse is cast on the target.

At higher levels. When you cast this with a 4th level spellslot the damage is increased to 1d6. With spellslots of 5th level or higher the AC of the target is lowered by 2 and still takes 1d6 extra force damage whenever the target is hit.