This one's going to be tough, because right now I have a four-way tie for first place. I'll have a think on this a while before deciding my final placements. (And voting has yet to open.... 😞)
Doctor Who, "Resolution"
I'm not really a Whovian as such; that is, I'm not one of the fans who's watched it for years and years and could describe every tic on David Tennant's or Peter Capaldi's faces. I did get interested when Jodie Whittaker took over the role, and watched a few episodes of her first season--I was particularly impressed by "Demons of the Punjab." I've also read a bit about the Daleks, but know very little of their storied history. So this was a sort of new antagonist for me, and I must say I wasn't overly impressed.
To be sure, part of this was the fact that the Daleks are what? Fifty-some years old, and created in an era when television special effects were decidedly primitive? Now, I know modern Who tends to revel in its cheesiness, and that was certainly in evidence here. But for crying out loud, in spite of all the Doctor's dire warnings about the Dalek, in its metal shell the thing looked like an overgrown, awkward, bumpy chess piece. I kept wondering why the Doctor just didn't angle the Tardis in and knock it over, because I couldn't see how it could get up. It was actually more frightening in its alien squid form.
(Of course, that led to the most cringey, facepalming moment of the entire episode, when the female guest star went to check out the odd sound, and spotted said alien squid perched on the wall. Then she proceeded to approach the squid--despite my screaming at my monitor, "OH FOR FRAK'S SAKE HAVE YOU NEVER WATCHED ALIEN OR ANY HORROR MOVIE EVER,"--and touch the damn thing.)
To be sure, the Doctor and companions succeeded in sloughing the Dalek off Ryan's father's back and into space--while somehow avoiding simultaneously dumping all of the Tardis's oxygen supply--but the entire storyline just seemed mediocre to me. The subplot with Ryan and his father was slightly more interesting, but the episode as a whole was simply not that good.
The Good Place, "The Answer"
I kowtow to no one in my dislike of The Good Place. I've tried to watch previous Hugo-nominated episodes, and more often than not couldn't finish them. These people are not funny or even likable, seeming to be more of a collection of exaggerated sitcom stereotypes than real people, and the dialogue doesn't sound like something even semi-real people would say. Having said that, I did finish this episode, but not because I liked the characters any better. Chidi appeared to be stuck at the age of eight until the very end, trying to logic, nitpick and intellectualize his way through life (no wonder his girlfriend walked out on him). I finally realized I liked some of the philosophical ideas the characters were presenting, but I wished said ideas were coming out of anybody but these people's mouths.
We Have a Winnah!
The Expanse, "Cibola Burn"
I nominated one episode of The Expanse Season 4, but it wasn't this one. It was episode 9, "Saeculum." This episode was more of a preparation for season 5 than a proper ending in and of itself. Not that it was't good--it certainly whet my appetite for the upcoming season 5--but I didn't think it represented the best of the season.
The Mandalorian, "Redemption"
Now this was a proper ending, directed by Taika Waititi in his trademarked action-packed, poignant and humorous style. We got a glimpse under Mando's helmet, and saw Pedro Pascal's face! Gina Carano really can act, and did a fine job here! IG-11 had an emotional send-off, and Mando accepted the responsibility of Baby Yoda, setting off at the end to find his people. This was the longest episode of the season, but all the payoffs were definitely here.
Watchmen, "A God Walks Into Abar" and "This Extraordinary Being"
Here we have two episodes from Watchmen's excellent first season, and they're neck and neck for me. "This Extraordinary Being" is more or less a standalone, telling the origin story of the vigilante superhero Hooded Justice, and "A God Walks Into Abar" is more of a love story, recounting the relationship of the show's lead Angela Abar and Dr. Manhattan. This entire first season, of course, is bound up in the history of race relations in America, and retelling the 1921 Tulsa Black Wall Street massacre. Now, of course, it is more pointed and necessary than ever.
Whew. This shows what an embarrassment of riches we have on genre TV and streaming these days, because I think this ballot--as much as I love Good Omens--walks all over the Long Form nominees.