Complete Disreguard

Whenever a creature enters the range of this spell or you pass close enough for a creature to enter the range of this spell, you may use your reaction to cast it. That creature must make Constitution saving throw or be reduced to dust and killed instantly. If a creature's maximum hit points is above 4 when you cast it, the spell fails.  If they are under the effects of a poly-morph spell, that spell instead ends and your spell has no other effect.

At Higher Levels: If you cast this spell using a spell slot of 1st level or higher, it instead only fails if the creatures maximum hit points is equal to 4 times the level the spell is cast at.