Calamitous Strike (5e Spell)
From D&D Wiki
|Casting time:||1 reaction, which you take when you hit a creature with a weapon attack|
You utterly obliterate the creature you hit with your attack. Instead of dealing normal damage for your attack, the creature you hit must make a Constitution saving throw, taking 20d10 damage of your weapon's damage type and 20d10 force damage on a failed save, or half as much damage on a successful one. This damage bypasses the damage resistances and immunity of any creature.