Previous Versions can be found here.

Termination is a Perseverance deck specific effect card which allows you to kill a monster under KR, including your own.

It's an incredibly useful card to get rid of something that's too powerful for Worsening, either due to their high HP or their ability. Most notable of this is Sans. (Mad Dummy can still be killed with Worsening.) It can also be used over Worsening on cards like MTT Fountain. Worsening deals damage which will activate MTT Fountain's ability. This card doesn't.

It is possible to use this card on monsters even if they aren't under KR. This can be useful if your hand is full and think you can afford wasting the Termination, but not the next drawn card.