Easy to make misstake, but it was Power Word: Pain, not Kill.

You speak a word of power that causes waves of intense pain to assail one creature you can see within range. If the target has 100 hit points or fewer, it is subject to crippling pain. Otherwise, the spell has no effect on it. A target is also unaffected if it is immune to being charmed.

I would not give an NPC a spell like that so I suggest this:

Power Word Incapacitating Tickles

You utter a word of power that can compel one creature you can hear within range to fall over squirming and laughing, begging you to stop the imaginary tickles until you choose to end it's effect. If the target has less than 100 hit points it takes effect, otherwise the target enjoys the sensation that feels like tummy rubs and is charmed for one round.

POWER WORD:
SHIT