Your consequence is an illusion. For neither death nor indignity are permanent punishments here-- and as I have said, and you have not heard, Sephiroth will take no lesson from this that you wish him to learn. He will not fear you or your impermanent reprisals. Likely, he will use knowledge he has gained through your actions against you in some way as yet unforeseen. In his place, I would do the same.

As to permission, I fear that one does indeed need the trust and permission of those one claims to champion, for such an act is a bond. But you have your vengeance. There is no need to pretend to some higher goal of protection, which is errant, and transparent, nonsense.

I do not fear you.
Like you, I will do what I must do.