Can Lightning Lure be used to knock out a creature like a magical Taser?

Now, before everyone starts in on its a strength save not an attack roll, or as it has a range of 15 feet is not a melee attack: Yes I’ve taken those rules into account when asking this.

So under the rules as written this is a strict no from what I can see, and I can live with that, but here is a hypothetical situation:

A creature is fleeing past you at 15 feet, you want to use lightning lure to drag it back and subdue it, it does not take damage till 5 feet away and all other criteria are met, but the lightning lure damage causes the creature to drop below 0 HP.

The question is could the caster drop the cantrip before the lightning damage actually killed the creature?