*counting on his fingers* The one that separates the soul from the body instantly -- Avada Kedavra -- the one that separates the soul from the body in gradations -- Cruciatus, and the one that stops the heart -- Petrificus Cardis.#
It's not an Unforgivable, and it's fallen out of use since the Killing Curse -- the contemporary Killing Curse, I should say -- was developed. But the effect on the caster is similar.
And if this victim is suffering from after-effects of the Cruciatus, then the treatment I suggested would no longer apply.
# I know cardis isn't proper Latin, but then again, neither is petrificus.