My go to reference for this is Search Party. The first season is the most engaging TV I've ever seen, the second season is still pretty damn good, but then the show got picked up by HBO and became total shit for 2 seasons. Like god I fucking hated season 4 of that show.
As far as movies go, I gotta go with Shrek the Third. 1,2 & 4 are all great, but what the fuck was 3?
Probably Heroes. First season was good, second sorta had potential but fell off pretty hard fast during it.
Heroes was a warning that capeshit typically is preoccupied with origin stories and rarely commits to going forward and actually putting a team together and keeping them on ongoing adventures, outside of the MCU thing.
Heroes is the classic answer