Dungeons & Dragons 5e Element 133 Class Feature: Execution

Your weapon is an extension of yourself, and you may take down even the mightiest of enemies with well-placed blows at an incredible speed.

As an action, if you have advantage on an attack roll, you can make an attack against a creature with one of your proficient weapons. On a hit, you force the target to make a Constitution saving throw. On a success, the attack is a critical. On a failed save, the target is reduced to 0 hit points. Creatures of large size or larger have advantage on the save. Creatures Huge or higher are reduced to half their maximum amount of hit points.

When a creature succeeds the saving throw against this ability, you can't target that same creature again until you finish a long rest.