No matter how unique an individual anime is, there are still several character tropes that appear in anime pretty often. One Piece and Naruto are both led by strong idiots, for example. Another common trope in anime is the super-genius. The geniuses of any anime are the ones creating plans, manufacturing spells and devices, or discovering the enemy's secrets.
No matter what happens, the smart guy or girl is always ten steps ahead of everyone else. The heroes, and even sometimes the villains, find victory because the geniuses helped them get there. However, no anime character is perfect and even geniuses can be tricked or surprised.
10 Hitsugaya Never Saw Aizen's Betray Coming (Bleach)
Toshiro Hitsugaya from Bleach is considered a prodigy. He is the youngest captain of the Gotei 13 or 13 Court Guard Squad, as well as the smartest. During the Soul Society Arc, he was the one who discovered that the members of Central 46, the central government of the Soul Society, had all been killed. However, all his intelligence didn't prevent him from falling for Aizen's betrayal. Hitsugaya was the first to discover the captain of squad 5 was a traitor but he was still nearly killed by Aizen.
9 Shikamaru Miscounted His Enemies (Naruto)
Not only is Shikamaru a genius, but he is also one of the smartest characters in any anime. He's almost never been tricked by an opponent and always stays a step ahead of everyone he meets. However, there is one moment where an enemy manages to get the drop on him. When Naruto, Sakura, and Shikamaru were chasing Gaara during the Chunin Exams, Shikamaru stayed behind to stall the sand ninja who were tailing them. He'd successfully trapped them with his technique but hadn't realized one ninja was hiding from him. If Asuma hadn't come and saved him, Shikamaru would have been killed.
8 Armin Was Forced To Sacrifice Himself (Attack On Titan)
Armin may not be the bravest, but he makes up for that with his intelligence. Even Erwin, the leader of the Scouts, looked to Armin for battle advice. However, Armin's brilliance couldn't account for every scenario the Scouts would come up against.
During the expedition to fill the hole in Wall Maria, the Scouts find themselves trapped and surrounded by Titans controlled by the Beast Titan. Outgunned and outsmarted by the enemy, Armin sacrifices himself to buy more time for Eren and the others. If it wasn't for the extra Titan Serum the Scouts brought with them, Armin never would have survived getting burned alive.
7 L Couldn't Comprehend The Existence of The God of Death (Death Note)
He goes by many different aliases but in the majority of Death Note's story he was simply known as "L." He is the world's greatest detective and was tasked with discovering the identity of the serial killer known as Kira a.k.a Light Yagami. L came the closest to discovering Kira's identity and his detective work was instrumental in revealing Light's true nature. However, even he couldn't comprehend the true nature of the Death Note and because of that Light was able to beat him.
6 Norman Never Could Have Imagined What Was Behind The Wall (The Promised Neverland)
Norman isn't the only genius from The Promise Neverland but when it came to tricks and schemes he usually took charge. That intelligence is ultimately his downfall because it makes him highly valuable food for demons. When the kids realized Norman is next on the chopping block they concocted a plan to get him past the wall that prevents them from leaving. The plan goes perfectly and Norman is able to climb to the top of the wall. Unfortunately, what Norman sees at the top of the wall isn't a way out but a cliff. With no way to the other side, Norman is forced to go back to the house and face the consequences of their failure.
5 Momo Yaoyorozu Was Outsmarted By Kendo
Yaoyorozu from My Hero Academia is the smartest student in class 1-A, often ranking at the top of the class. She struggles with low self-esteem but even that doesn't stop her from coming out on top.
During the Joint Training Arc against class 1-B, she comes up with a brilliant plan to defeat the other team. However, even she couldn't account for class 1-B's Kendo's intelligence. Yaoyorozu is able to slow Kendo down but her team ultimately loses to Kendo's superior battle tactics.
4 Senku Ishigami Underestimated His Enemies (Dr. Stone)
Senku is a genius tasked with restoring civilization. He comes off as arrogant but he has a right to be, considering he discovered a cure that can save the world. However, his overconfidence often leads him to make rash decisions that end up backfiring on him. When he and Taiju were attacked by a lion they revived Tsukasa, who just happened to be nearby. Tsukasa joined them as an ally until Senku realized Tsukasa intended to kill every adult in the world. In order to stop Tsukasa, Senku attempted to trick him. However, Senku underestimated Tsukasa's intelligence. Tsukasa discovered Senku's trick almost immediately and because of this, Senku was forced to give Tsukasa the recipe for the revival fluid.
3 Koro-sensei Had To Use His Last Resort (Assassination Classroom)
Koro-sensei presents himself as a super strong and super-intelligent alien who is all but impossible to kill. He is also overconfident, which makes sense considering how hard it is to trick him. However, that overconfidence nearly leads to his downfall during the Assassination Island Arc. It is the closest the students ever get to assassinating Koro-sensei. They successfully trick him into weakening himself by shedding his skin and they manage to trap him inside of a hydraulic water cage. The only thing that saves him is his ultimate defense form, which is supposed to be used as a last resort.
2 Light Yagami's Ego Made Him Slip Up (Death Note)
Light Yagami is incredibly intelligent for his age, making him the worst person to find a Death Note, capable of killing anyone whose name is written inside of it. With the power of the Death Note, Light adopts the name Kira and begins killing criminals en masse. The police try to stop him but even the brilliant detective L eventually loses to Light. However, the power of the Death Note messes with Yagami's head. He starts thinking about himself as a god. During the final confrontation Light preemptively declares victory, not realizing he's being tricked. His downfall is ultimately caused by his own hubris.
1 Nico Robin Was Tricked By The World Government (One Piece)
Robin is the smartest member of the Straw Hat pirate crew. Her intelligence puts her in danger during the Water 7 and Enies Lobby Arcs. The government group known as CP9 decides to use her intelligence to create a weapon that will put an end to the pirate age. In order to get Robin's cooperation, CP9 promises her that the Straw Hat Crew will not be harmed. Once she arrives at Enies Lobby the chief of CP9 reveals that he has no intention of fulfilling CP9's promises.