Electric Rebuke

The creature that damaged you finds themselves instantly surrounded by crackling electricity. It makes a Dexterity saving throw, taking 2d10 Lightning damage on a failed save or half as much damage on a successful one. In addition, on a failed save, the target must also make a STR or CON save, with no effect on a success, but on a failure gains the Stunned condition until the end of their next turn.

Using a Higher-Level Spell Slot. The damage increases by 1d10 for each spell slot level above 1.