15. Season 1

Like many shows’ beginnings, Season 1 of “It’s Always Sunny in Philadelphia” is the weakest entry in the series, as the sitcom struggles to discover its unique voice.

The season isn’t terrible, but it’s clear that the writers are still figuring out how to depict the characters as horrible people without inadvertently valorizing them.

14. Season 11

Initially planned to have only 10 seasons, “It’s Always Sunny” was renewed for Season 11, though the show seemed to be off its game this season.

Season 11 does have its highlight episodes like “The Gang Hits the Slopes” and “Mac & Dennis Move to the Suburbs,” but it also produced the worst one — “Being Frank.”

13. Season 2

Although the show’s writing is still trying to find its voice in Season 2, the addition of Danny DeVito as Frank Reynolds to the cast took “It’s Always Sunny” to a whole new level.

Before Frank fully embraces his wildest impulses in later seasons, he begins as a stand-in for the beleaguered straight man, a role that would pass to the secondary characters.

12. Season 10

While it wouldn’t be fair to say that the show was “grasping at straws” in Season 10, it does feel like “It’s Always Sunny” is close to hitting a wall with its formulaic episodes.

However, this season has one of the series’ greatest episodes: “Charlie Work,” a character-driven story that shows why Charlie is the glue that holds the gang together.

11. Season 14

Season 14 suffers from the same formulaic, mid-tier quality as the previous entry, but it also has the unfortunate luck of being sandwiched between two fantastic seasons.

The finale, “Waiting for Big Mo,” is Season 14’s highlight, which shows that the gang will never change in this bleak episode that could serve as the series’ spiritual finale.