Even some of Solo Leveling seem to only get better the longer they're on, that isn't the case for everyone. Some series seem like they're doing everything right, only to drop the ball during their second or third seasons.

Having a terrible season in the middle of a great series hurts even more than an all-around terrible anime because it makes fans wonder what could have been. Some series are able to recover from their lows, but other series become synonymous with their worst moments, showing just how important it is for a series to maintain its quality throughout its runtime.

10 That Time I Got Reincarnated As A Slime

Animated By Eight Bit, Based On The Light Novel By Fuse And Mitz Vah

That Time I Got Reincarnated as a Slime is one of the best isekai series of all time, and somehow, its third season nearly ruined everything. The series stars a former Japanese man reincarnated as a slime in a new world. While slimes are almost always the weakest monster in any fantasy series, Rimuru Tempest is the exception. He's so absurdly powerful, he's able to start and defend his own nation.

The third season of That Time I Got Reincarnated as a Slime is so surprisingly bad that it feels like it belongs in another franchise. Commonly referred to as "That Time I Got Stuck in a Meeting" or "That Time I Got Reincarnated in a Meeting", the season is so fixated on meetings that it feels like the series is messing with its fans. In a series defined by action, the third season of the isekai takes all the excitement out of the franchise.

9 Tokyo Ghoul:re

Animated By Pierrot, Based On The Manga By Sui Ishida

Tokyo Ghoul is one of the most beloved anime series ever, which makes Tokyo Ghoul:re's fall off even more disappointing. The original series is ranked as the 10th most watched anime series of all time on MyAnimeList.com, one of the biggest anime forums on the internet. The sequel to Tokyo Ghoul, Tokyo Ghoul √A, isn't too far behind as the 59th highest-ranked series. Both series also have 7.79/10 and 7.02/10 scores respectively, two great scores for the franchise.

Tokyo Ghoul:re unfortunately doesn't share the same accolades. It's outside the top 1000, ranking as the 119th most popular series, and carries a low 6.37 rating. Fans consider Tokyo Ghoul:re to be confusing, awkwardly paced, and underwhelming. It's a sad change of events from what started out as a powerhouse of anime. At least the first few seasons are solid, but it would have been even better if the entire franchise was as great as it began.

8 The Saga Of Tanya The Evil

Animated By NUT, Based On The Light Novel By Carlo Zen And Shinobu Shinotsuki

The Saga of Tanya the Great is one of the most entertaining and unique isekai series of all time. The series stars a normal Japanese man as he's killed by a coworker. While he's dying, he claims that there is no God in the face of a creature claiming to be exactly that. "Being X", as the man describes the entity, reincarnates the man in a new world as Tanya von Degurechaff.

Tanya soon dominates her world ferociously as one of the youngest and smartest characters in it. While both seasons of the series are solid, the movie is terrible. Saga of Tanya the Evil: The Movie is a pretty great entry into the franchise until it introduces Mary Sioux, one of Tanya's mortal enemies. One of the worst tropes in anime is when a character dies only to be revealed to be alive yet again.

Tanya and Mary have a great fight, and it seems like at least one of them had to have died from the intense fighting. Unfortunately, neither of them died, making the entire fight seem entirely meaningless. It's a underwhelming and frustrating end to what could have been a great movie.

7 Banished From The Hero's Party, I Decided To Live A Quiet Life In The Countryside

Animated By Wolfsbane And Studio Flad, Based On The Light Novel By Zappon And Yasumo

Banished From The Hero's Party, I Decided To Live A Quiet Life in the Countryside had the potential to be one of the best romance series of all time. The first season introduced a fun and unique concept to the art form, setting the scene for a great season. The series is about Red, a character kicked out of the hero's party who decides to live a quiet life of peace instead. He meets Rit after opening his own shop, and the two quickly fall for one another.

The hero and Red's sister, Ruti, make her way to her brother's shop and lives with him at the end of the first season. The second season could have capitalized on the first's success, but instead, it chose to introduce an unlikable villain and pitted Ruti against him for no reason. The series could have delved deeper into Red, Ruti, and Rit's new life, and it would have made for a great continuation of everything the first season put forward.

6 Fire Force

Animated By David Production, Based On The Manga By Atsushi Ohkubo

Fire Force was one of the hottest anime series when it first came out in 2019. The 2020 sequel and second season took everything that the first season put forward and ran with it, creating a great adaptation of the manga that the anime is based on. Fire Force is a simple shōnen anime with great fights, amazing animation, and some of the best sound design in the entire art form.

The third season didn't come out until 2025, snuffing out all the momentum the first two seasons worked hard to create. While the third season of the series looks to bring the same high-powered fights to the franchise, it doesn't feel the same. The moment is gone, the pacing is off, and it struggles to keep up with the edge the first two seasons brought to the table. The third season feels rushed, which is ironic considering how long it took to come out.

5 One Punch Man

Animated By Madhouse And J.C. Staff, Based On The Webcomic By ONE

One Punch Man's second season was a huge letdown to anime fans across the world. The second season itself wasn't horrible, but compared to the masterpiece that was the first season, it wasn't a worthy successor. One Punch Man has one of the simplest premises in anime: what if a character could defeat nearly anyone with a single punch? It's one of the funniest anime of all time because of where it starts, but unfortunately, the second season takes a different direction.

There are two main problems that plague the second season of One Punch Man: the series doesn't focus on its main character and a new animation studio took over. Madhouse is one of the best studios in anime. They created the first season, but were too busy for the second. J.C. Staff came in for the second season and let a ton of fans down.

4 Overlord

Animated By Madhouse, Based On The Light Novel By Kugane Maruyama And So-Bin

Overlord is another solid isekai series with a great premise that makes the show entertaining from the start. The series stars Ainz Ooal Gown as he finds himself trapped in his favorite video game. Luckily, Ainz is one of the strongest characters in the world. Where other isekai characters might come to their new world with the hope of improving it, Ainz looks to be the titular Overlord, dominating his enemies through conquest and power.

Overlord has four seasons; the first, third, and fourth are almost perfect. The second season is so bad that it feels like an entirely different show at times. The second season of Overlord rarely focuses on the main cast of characters, instead highlighting a random group of lizard people that have nothing to do with the main story. There is a fun battle scene where Ainz eventually subjugates the lizards, but that's about it for nearly 15 episodes.

3 Shangri-La Frontier

Animated By C2C, Based on the Web Novel By Katarina

Shangri-La Frontier isn't the first anime series to take place within a video game. Whether or not it can truly be called an isekai series doesn't really matter either, because Shangri-La Frontier is amazingly entertaining from the very beginning. The premise of the show is that an expert video game player who normally plays bad games finally plays one of the best, quickly becoming one of the most unique characters within his new game.

Because Sunraku chooses to forge his own path, unlike other players, he uncovers some of the most interesting parts of the video game he's playing. For whatever reason, the second season betrays everything put forward by the first, forcing Sunraku to play a more servant-like role to the guild masters of the game he's in. It's a change that makes the series do a complete 180, ruining what could have been an exceptional series.

2 Tower Of God

Animated By Telecom Animation Film, Based On The Manhwa/Webtoon By S.I.U.

Tower of God's first season brought one of the longest and most popular webtoons to mainstream anime viewers across the globe. It stars Bam climbing the titular Tower of God, trying to find himself, his best friend Rachel, and whatever is on top of it all. The first season had a lot of great things going for it. The most captivating aspect of the first season was the incredible art style, showcasing the main characters in a form unlike any other series in anime.

The second season of Tower of God took several steps back in of quality. First and foremost, the art style changed from top to bottom, reverting to a normal, run-of-the-mill style. Second, there was barely any animation at all, as Tower of God began to look more like a PowerPoint presentation than an actual animated series.

1 The Promised Neverland

Animated By CloverWorks, Based On The Manga Written By Kaiu Shirai And Illustrated By Posuka Demizu

Unfortunately, the only time people talk about The Promised Neverland is when they're referencing how bad the second season is. The first season of The Promised Neverland was promising to say the least, showcasing an interesting premise, adorable characters, and one of the most gripping premier episodes in anime. The series starred a group of intelligent kids in an orphanage as they quickly and brutally learn that the world they live in has a dark twist to it.

The second season of The Promised Neverland made such bad decisions that it is baffling. The anime adaptation skipped arguably the best arc in the entire show, omitting key characters, plot points, and creating massive plot holes at the same time. The writing felt worse, the characters' decisions didn't seem to make sense anymore, and the show as a whole felt like it abandoned everything that made it great.