What are some shows that recovered from the sophomore slump?

[Benji]

Maybe they didn't return to full form, but they gave a cromulent ending and were compelling before the end.

Homeland is a big one for me...

Spoiler

I don't blame anyone for quitting after season one, or even when Brody is killed off, but honestly the show really found its way back into a great final few seasons and I feel like people had tuned out by then to appreciate how good it was. Even I quit the show for a while and only caught up later because I'm a completionist.

 

[GoGo Yubari]

Friday Night Lights, albeit because their second season was a) cut off by a writer's strike and b) almost completely disregarded when they came back for season 3. For the most part I agreed with that decision, though I thought the choice to basically act like Santiago (a perfectly fine character!) never existed had some incredibly unfortunate implications.

[livid]

Mr. Robot is the first one that comes to mind. I didn't hate S2 as much as most but S3-4 are more on par with what made the first season so successful. I've actually been thinking about revisiting it now that there's some distance from when it ended so maybe this will motivate me to do that.