For a grand finale, this episode is a real let down. Not only does it have its fair share of padding to fill out the run time, but the big battle that's been hyped since the very first episode is incredibly anti-climactic.
I was wondering what was going to happen to Arashi and, sure enough, she does appear to apologize for maiming Kusanagi. Yuzuriha does forgive her, because she's nice like that. The scene also establishes that Arashi has lost her powers, why? No idea. I guess my "injury" logic didn't hold up. The only thing I can think of is that their powers are tied to the barriers, which were being broken? Maybe? It's more likely that the plot just demanded it, but some explanation would have been nice. Speaking of barriers, one of them was called the "Rainbow Bridge". I chuckled at that due to the likely unintentional Thor reference.
The one on one fight between Kamui and Fuma is also a let down. Kamui doesn't really put forth much of an effort and ends up getting impaled twice. Subaru, to his credit, does do what he can to assist Kamui, coming to his aid before Fuma was about to deliver a killing blow, but there isn't really much of a confrontation. Considering this was supposed to be the big fight between good and evil, one that was set to determine the fate of the planet, it's really disappointing.
Even more disappointing is the resolution. Kamui dies and he wishes to live on in Fuma's heart or something and that brings him back to normal. It's not quite "power of friendship", but it comes really close. I get wanting to bring Fuma back to his old, kind hearted self, but they could have found a better way to do it than that.
It's pure deus ex machina. They wrote themselves into a corner and needed to pull something out of a place where the sun doesn't shine.
Honestly, I would have liked to see the Dragons of Heaven come together as a team. Fuma may be vastly more powerful than them, but they could have turned the tide. It happened all the time on "Young Justice", they could have done something similar here where coordination and teamwork overpower brute force.
Even if you wanted Fuma back, you could say that the aversion of the prophecy was enough to free Fuma's mind from whatever was controlling him before. It would have been a lot more satisfying than what we got.
On the plus side, the Earth is saved and those who are still living do find some measure of peace in their lives, enough to move forward if nothing else.
The show aimed high, going for something epic, something of Biblical proportions. It had its moments and was, more often than not an enjoyable watch, but alas it ends, not with a bang, but with a whimper.