Most of American shows tbh.

Stranger things. Season 1 was perfect, 2 & 3 were mid except for the nostalgia factor. I’ll die on this hill.

Stranger Things would have been a perfect anthology show too, while still getting to explore the in universe lore.

Heroes

Idk if this is the worst per se but a good example is Russian Doll.

When I see questions like this I'm not just thinking of shows that had a good first season but then a step down in quality. There are lots of shows like that.

I'm thinking of shows where the first season completely stands on its own, perhaps even intended to be a miniseries, but for whatever reason a second season is greenlit.

Russian Doll had a fantastic first season that told its own story. The second season just felt unnecessary and was pretty forgettable.

The Handmaid's Tale would've been a much tighter story.

Westworld goes without saying.

Prison Break.

Squid Game.

Altered Carbon

Broadchurch.

Such an amazing show with an excellent cast. Deeply thrilling and moving, difficult to watch at times but totally compelling. Came out at a time where the idea of binge watching shows was relatively new and really hooked you in the tragedy and mystery of the story.

The second and third seasons just failed to capture what made the first so compelling. Decisions made in those seasons actively took away from the first season for me, though I don’t want to say much for spoilers-sake.

I would still recommend it 100%, but definitely tough to watch as the subject matter does include bad things happening to children.

The Bear. Season 1 was a fresh mix of fast paced foodporn and insult comedy. Now its just people sitting around depressed, never being funny nor going anywhere. Like, family anxiety porn? As if anyone actually wants that.

Knights of Sidonia. First season was dark, bleak, gritty. Mystery and intrigue, and kick-ass action.

Second season turned into a dating sim, complete with horny AI spaceships. I wish I was joking.

Yall know they made a second season of Tiger King? It's just as stupid as you'd think I gave up like 1 episode in

Twin Peaks, it was supposed to only be one season, but they forced it to go another season, so David Lynch just stuffed the second season with pointless bullshit until the last couple episodes and then did what he intended to do in season one. You can skip almost all of the second season and not miss anything, literally nothing matters until the end.

Westworld! By far!

Servant. The drop in quality and atmosphere between season 1 and the following 3 is beyond baffling. Goes from psychological thriller to sitcom very quick and I felt sorry for the cast by the end.

Yellowjackets. Extremely tight, well plotted season 1, with an amazing cast. By season 2 the writers had dropped the ball so hard, cast members started complaining publicly and/or just leaving the show. It's probably the most egregious example I can think of of writers promising a 5-season plan while so clearly and unapologetically making shit up as they go.

Chuunibyou. First season had a fantastic ending, then they decided to make a second season that undoes all character development in order to introduce a dumb love triangle.

And while S2 isn't even out yet, I'm already disappointed that I'm in Love with the Villainess set up what should've been a perfect ending but then didn't commit in order to leave it open for a S2.

Jessica Jones

The news.

The Matrix

Yeah I know

Bed time children. I can't believe nobody mentioned Twin Peaks.

Joel did such and fantastic job with the character. His acting and the writing gave the character and show so much depth that the second season completely missed. With Anthony Mackie it was like trying to watch an entirely new character pretending to be Kovacs the whole time. Totally botched the entire concept of the show.