True, about Pieta Battle, but I'd say that's a bit of a special and "stand alone" case, as at least half the purpose of the Pieta Battle was a way of the Org to "cleanse-purge" (execute-kill off) those "Troublesome" 24 Claymores, without having their own "hands stained or being able to be accused of their actual intent of malice".
and if you want to get more technical... Clare should have been dead (or Awakened) many many many times, too. Clare has technically "come back from the grave many times".
My statement was more in this loose-general manor and not so specific or technical or special cases-exceptions as there are.
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and again, the point of my (badly done-used) statement is that of the literary, poor writing-story telling.
you can only use a surprise once. If you have a haunted house full of surprises, all of those additional "surprises" aren't surprises, as you're now ready for them or aspecting them more and more with after each additional surprise. Same with a horror movie too, the more surprises, the less you are surprised ("jump up in your seat") by them.
this applies to writing-story telling, to literary.
having a character "come back from the grave" is a surprise, but do it a second or third or fourth, becomes very lame and boring (DBZ, Bleach, Naruto, and etc... with their "Insta-magically" power ups after a beatdown, over and over). thus, it is very bad writing-story telling to have a character "come back from the grave twice or more times".
Aizen being revealed as the villain was excellent in Bleach, but what if there was another such plot twist and another and another, they'd not have that same excellence, that same shock value, as did Aizen's revealing as being the villain.
Irene being revealed to have actually survived Priscilla was excellent, NO ONE could have foreseen-guessed that, as there wasn't anything for us to know, hehe.
Having Irene still alive after Rafaela, would just be lame. Irene has already fulllfilled her purpose, let her "Exit in glory", same with Teresa too, let Teresa remain dead, as the Legendary Ultimate Being, even more powerful than Awakened Priscilla, hehe :D
Renee could be brought back like Irene was, but I just don't see how it could be done for significant purpose, in how it could be done well... Irene's "comeback" was excellent and significant... saving Clare from trully about to being killed by Ophelia, hehe, and then in cheering up Clare about being responsible for Teresa's death, and finally in teaching Clare the QS, Yoki Focusing Ability, and giving Clare her Arm, so that Clare again has two arms.
The same applies to Riful as well... I don't see any way for Riful to be "brought back" with any type of significance, in a well-done way...