For me, Arya killing the Night's King doesn't feel earned. She has zero history with the character and it came out of left field and It didn't really make sense to me thematically. It's like Hawkeye duking it out with Thanos, when it should be Tony Stark in the end.
I think where this misses the mark is in treating the Night King as a character with which one can have a rivalry. He isn't. Like any good zombie, he's a force of nature. You don't get angry at the plague. You just stop it by any means. His origin doesn't matter. The fact he killed your friends or your dragon doesn't matter. Nature kills all the time and nature is older than dirt, so the origin might be interesting, but it won't be useful.
The dude's only expression of emotion (or anything really) in the entire series was after surviving dragon burnination unscathed. And it was a smirk. A half hearted one. Perfect.
As an opponent, they handled it well. The big army was a hindrance in the end. The dragons were easily sidelined. The strategy wasn't all that useful. In the end, what won the day was a little slight of hand from a character no one expected, but looking back makes perfect sense.
I wish, really wish, TBTP had treated the Borg this well over the years.
Even that doesn’t really work. Should have been Nebula
Haven't seen this movie, but that's what I'd have expected narratively. Yet, I'm not surprised it went down this way. Nebula never gets what she wants. Iron Man always saves the day. meh. I don't watch those movies for plot.
Speaking of narrative expectations, this episode really should have been the last one. Cersei as the last boss? Nah, son. Especially as this proves her decision to hold out as correct. She's left facing a far smaller opposing army while her forces (such as they are) remain intact. Does that matter facing two dragons? No, not really. Last season showed that. However, it's not like she was going to be allowed to remain queen anyway, so why not play for keeps?
They've been pretty consistent about Cersei's shortsightedness ultimately dooming her. Shame if they gave up on it in the last stretch.