Cremation

You point at a creature within range that you can see, the target creature becomes awash in bright and radiant flames and must make a dexterity saving throw, taking 3d8 radiant damage on a failure or half as much on a success.
Any creature that reaches 0 HP and dies from this spell, has their body destroyed and turned to ash, and cannot be resurrected except by the means of a true resurrection or wish spell.

Alternatively, you can target any number of corpses within range that are dead, and ceremoniously cremate and destroy the bodies

At higher levels: for every other level above 2nd that you cast this spell, you may target an additional living creature.

"In the end, let none be but ash..."