Thunderstorm Haymaker

You wind up and deliver a full-force punch backed by the explosive power of a thunderstorm. Make a melee spell attack against a creature within reach. On a hit, the target takes 8d10 lightning damage and is stunned until the end of your next turn.

Additionally, the kinetic energy of the punch creates a shockwave. Every other creature of your choice within 10 feet of the target must make a Constitution saving throw (20 DC), taking 4d10 thunder damage on a failed save, or half as much on a successful one.