...IDK. the fucking voyeur being the ultimate "fuck you" to everything everyone was fighting for feels kinda deserved because, unlike everyone else's reason for wanting to be destroy the world, it felt like the most bastard and petty motivation for it. Which works for how selfless our protagonist is, to have someone so delusional and egotistical to be the one who actually confront him in the end.
If only they actually had him running around the background, hiding cowardly from everyone, and we could have seen him biding his time, it would feel a lot better when he appear to fuck everything up, but he didn't and christ the author can be felt running on fumes with how everything plays out instead. An interesting idea done way too late, and way too clumsily at that.
In other stuff, the mix of black and blond hair in the MCs' combined form after the sister gives them her power is cool, and the angel wings I guess is because of that too because they're bringing hope? Whatever, works for how the author is trying to play all that, but now we have to wait and see what they're actually going to do. Feels weird to think that banishing the fucker actually clears the fake Honoka's whatever that remains in the world, but if the power of the three together manages to do so, they well fucking deserve it with all that has happened by now.
And if not, our boy still has the chance to be the Gleipnir after all...