Power Word Kill
Casting Time
Range
Target
One creature
Components:
Duration:
Instantaneous
With but a word you snuff out the target’s life and it immediately dies. If you cast this on a creature with more than 100 hit points, it takes 50 hit points of damage.
Rare Versions
Roav’s Sacrificial Power Word Kill. When a target dies from the effects of this spell, you may use its life force to save yourself. For the next 8 hours, the first time you would drop to 0 hit points or be outright killed, you instead drop to 1 hit point. Once this effect is used, the life force is expended and the effect ends.
The Mouthless One's Power Whisper Kill. A creature within 60 feet that the caster can see takes 100 damage. If the damage reduces the target to 0 hit points, it dies.
Source