Even though there are a lot of episodes like this, I'll put the most failed episode from each season:
1. Pizza Delivery (Meh)
This episode has potential, and some funny moments here and there (especially at the ending), but the rest of the episode is mostly bland and the jokes aren't really helping. It's a meh episode, but could be done better.
2. Life Of Crime (Meh)
This is one of the episodes I refer to as a "stilted" episode, meaning that its story is good but the plot that supports the story is very weak. In a similar fashion to Model Sponge, this episode reveals that it's Free Balloon day too early, and the episode would have been better if they did not reveal that it was Free Balloon day until the end. Other than that, the jokes are pretty good, but they don't help much in improving this episode.
3. Squilliam Returns (Bad)
This episode really could've worked out, but it fails to do so. Again, it would be nice to see Squidward win like in Band Geeks, but Squilliam still wins in the end, leaving the Krusty Krab in chaos, Squidward depressed, and SpongeBob forgetting his entire life. Surely, the middle parts had some decent jokes, but other than that, this episode isn't really worth rewatching (unlike House Fancy or Band Geeks) because you know Squidward won't get a good ending and Squilliam will still win.
4. Have You Seen This Snail? (Very Bad)
Probably the worst one on my list now, Have You Seen This Snail could be a fantastic episode, but it is a garbage fire. The pacing is the worst issue here, and it destroys the entire episode's flow. The first half is mostly filler with the paddleball set, and BORING filler as well. SpongeBob and Patrick do not even notice Gary runs away until the SECOND HALF of the episode! Then we get a few minutes of boringness with SpongeBob depressed and going everywhere to find him. And after that, there's the Gary Come Home song. It is one of the BEST songs in the series, but placed in such a garbage episode like this, the song fails to even improve this episode's rating.
And the ending... that is the crown jewel of this ScumBob episode. The terrible pacing has taken its toll on the ending, which is extremely short and too short to generate any heartwarming moments. Seriously, the ending is less than 30 seconds, and if this episode was paced better, it really could become one of the best of the show.
5. To Save A Squirrel (Bad)
Nobody really talks about this episode...like other episodes such as Stanley S. Squarepants and Le Big Switch, I never seem to see anyone discuss this episode. Mostly because it is BORING (not many jokes or action), REPETITIVE (SpongeBob and Patrick trying to cook each other, seriously writers?), and Sandy dressing up as the old man felt very lazily smashed into this episode. Nothing much else, but if the episode actually was a survival episode, it would've gone much better.
6. Professor Squidward (Bad)
Another episode with potential. Squidward gets tortured and sent to jail, while Squilliam and his ugly unibrow laughs at Squidward just because he wanted to become famous. It's Season 6, so you'd expect Squidward to never win at the end.
7. SpongeBob's Last Stand (Very Bad)
Oh god...I absolutely despise this episode. Another PLANKTON episode, which are 99% all of the episodes in Season 7. And Plankton had to be unnecessarily put in, and this episode had to be a special. The Bikini Bottomites are idiots who don't care about the environment, and I actually want to see SpongeBob and Patrick move away out of Bikini Bottom and let the city crumble into pieces. The songs are annoying and pointless, and everybody being idiots makes this episode unwatchable, and I nearly quit the show when I first watched this abomination. It really could be great, like Have You Seen This Snail?, but it's Season 7, and it's another dumpster fire.
8. A Friendly Game (Very Bad)
Part of the "very bad" rating in this episode goes to the extreme potential wasted in this episode. The mini golf theme really could've made this episode work, but it's Season 8, so we get Squidward Torture, Jerky Patrick, boringness, filler, and annoying scenes to watch. The part when SpongeBob and Patrick start the course starts off well, but as soon as the balls fly into Squidward's house, the episode goes bad faster than the bus goes down into Rock Bottom. Filler, annoying Patrick, and nearly 5 minutes of going around doing nothing that could've been used to turn this episode great. And after that, the episode ends with barely anything else going on. An episode with a lot of potential, but was executed in the worst way possible.
9A. Bumper to Bumper (Bad)
The first Mrs. Puff episode on my list, the episode had jokes such as the 3D show one, but the rest of the episode is stupid. Mrs. Puff scolding SpongeBob is painful to watch, and so is most of the rest of the episode as well. SpongeBob depressed in his house brings up SpongeBob You're Fired flashbacks, and the most infuriating part of the episode of all is how close SpongeBob was to passing, then some random c**p happens and he fails. AGAIN. Even if SpongeBob's license gets taken away somehow at the end, it would be nice to see him pass for once using Mrs. Puff's new strategy, but he still fails...as usual.
9B. Bulletin Board (Bad)
This episode could've worked out well, but Patrick being out of character, Bubble Bass being idiotic, and everyone else not caring that much makes this episode pretty bad, but at least there are some jokes and a decent ending.
10. Snooze You Lose (Meh)
The episode itself is ok, just the ending could be changed to improve it. It would be nice to have Squidward wake up and realize that SpongeBob and Patrick had helped him win the audition, but he loses as usual- a missed opportunity. Other than that, the episode is OK.
11. Fun-Sized Friends (Bad)
This episode's ending is probably one of the best endings of the entire show, but the rest of the episode...is GARBAGE. Flaming, burning, garbage. We get unnecessary Squidward Torture both at the beginning and at the end, SpongeBob and Patrick getting beaten up by their own little friends, and Mini SpongeBob and Mini Patrick getting tortured by SpongeBob and Patrick as well. An entire episode full of character torture, whether it's Squidward or SpongeBob and Patrick or their little dudes. The ending where SpongeBob and Patrick being nice to their little dudes really was beautiful, but when placed in such a stupid episode, it is only a reminder of the good concept wasted.
12. A Cabin In The Kelp (Meh)
I don't really understand why some people like this episode so much, it really is mostly boring with filler, such as the SpongeBob and the peanut parts. It could be a decent episode, but it's Season 12, so that probably won't come.
That was a lot...30 minutes spent typing this but it's finally done!