Avada Kedavra

You utter the words Avada Kedavra while pointing your finger, wand, or staff at one creature you can see within range, compelling it to die. Make a ranged spell attack against one creature you can see. On a hit, and if the target has fewer than 100 hit points, it dies. Otherwise, it takes 8d12 Psychic damage.

Using a Higher-Level Spell Slot. There is no hit point limit when the spell is cast using a 9th-level spell slot.