Grim Scythe

The harvestman has a duty to the harvest, as the inevitable caress of the scythe must be clean and painless.
A hooded figure wielding a massive scythe appears at your shoulder, and strikes with smooth certainty at a creature within range. The creature must make a Charisma saving throw. If they fail, the scythe cleaves into their soul, inflicting 10d4 necrotic damage. If this damage reduces the creature to 20 hit points or fewer, they are instantly slain. Once the attack is made, the figure vanishes.

At Higher Levels: When you cast this spell using a slot of 4th level or higher, the necrotic damage increases by 1d4 and the hit point threshold increases by 5 per slot level above 3rd.