[RPG] Are there any melee alternatives to Power Word Kill

dnd-5emelee-combatspells

The 9th Level Enchantment spell Power Word Kill outright kills any creature with less than 100 hitpoints.

I've had a look, but I can't see anything that would be similar via any melee action of feat, creature-, or PC ability.

So my question is: Is there anything that allows a melee attack to strike down a foe to either 0 hit points (rolling death saving throws) or outright kill them using one attack?

Effects with saving throws would also answer the question.

Best Answer

There's a class of legendary magic weapons, Vorpal Swords:

When you attack a creature that has at least one head with this weapon and roll a 20 on the attack roll, you cut off one of the creature's heads. The creature dies if it can't survive without the lost head. A creature is immune to this effect if...

It has a bunch of limitations, but against most creatures it has 1 in 20 chance of instantly killing your opponent.