The diversity of the characters that are in Attack on Titan are immense. No one ever feels similar to someone else, all of the characters having their flaws and goals in mind. It's part of what makes it such a great series, along with the depth of the plot. It very easily could have just been giant titans fighting each other, but the story is far more than that.
There's diversity even among the titan users, some of them being as easy to manipulate as a ball of clay while others had the intelligence of a grandmaster in chess. Which of them was the smartest of the bunch?
9 Grisha Yeager Lacked Self-Awareness & Had Many Of The Same Flaws As His Son
Grisha had a profound lack of self-awareness, unable to see the consequences of his actions unless they struck him square in the face. It's what causes the wedge between him and Zeke and eventually led to his downfall. He was also very weak-willed, always succumbing to the wills of those with a more dominant personality. He was nothing more than a pawn for the length of the story, not even knowing what his own goals were anymore.
8 Karl Fritz Was A Man Who Only Knew Guilt, Doing Anything He Could To Absolve Himself Of It
Karl Fritz bore the guilt of the many atrocities that Eldia committed on not only Marley but the world. Even before he gained the Founding Titan's powers, he only wished to make things right. His way of doing that was by creating the walls, giving Eldia a paradise for them to live in – that is until the other nations of the world swarmed them to force Eldia to pay for all of the sins it had committed. It was a very warped sense of logic.
7 Eren Yeager Was Too Impulsive & Angry To Think Rationally
Despite Eren being the main character of Attack on Titan and the cause of many tragic events that happen later in the series, he's never been an overtly intelligent character.
He gets by more on his charisma than sheer intelligence, using the force of his personality to rally people to his cause. The main thing always holding him back was his temper and inability to think things through. He's a slave to his impulses, unable to think rationally.
6 Falco Thinks On His Feet & Doesn't Panic Under Pressure
When he first showed up, Falco didn't seem like anything special. He didn't possess the typical soldier's attitude or physique, and he struggled to voice his opinions. That shifted throughout the series, showing just how smart he was. He excelled at improvisation, able to think quickly on his feet and talk his way out of any situation. He managed to explain why he and Gabi were alone in the woods and even figured out that his Jaw Titan could fly, something no one else knew was possible.
5 Reiner Was A Strategic Thinker Who Suffered From His Mind Being In Constant Battle With Itself
Reiner is a fascinating character who has such a depth of personality to him. He once had intelligence on the battlefield that matched Zeke's – he could predict people's movements and the consequences they would bring, always thinking in the long term rather than the short. However, his time in the Eldian military slowly began to break him down mentally, eroding that mental fortitude away and forcing him to struggle with who he truly was. His two personas began to clash, causing him to debate suicide.
4 Armin's Mind Helped Make Up For His Lack Of Physical Gifts
As with Falco, Armin never had the body to be a typical soldier. He was frail, lacking the physical gifts needed to excel, making him doubt himself in the process.
It wasn't until later that he realized how important his intelligence was, seeing how he could contribute in a different way than his friends. His biggest strength was his out-of-the-box thinking, allowing him to come up with strategies no one would expect. It made him a difficult tactician to deal with.
3 Pieck Finger Has A Great Power Of Deduction
As a member of Marley, Pieck doesn't get to show off her intelligence until the latter half of Attack on Titan, but she's shown to have great deduction skills. She's able to rationally come to conclusions based on what she's seen, as shown during the warrior meeting. Zeke Yeager even states that it's not an uncommon occurrence, showing how sharp her mind is. It's part of why Marley decided to give her the power of the Cart Titan. They trusted her to make the most use out of it.
2 Annie Is A Tactical Thinker Who Knows What Her Strengths & Weaknesses Are
What sets Annie apart from many of her other titan users is the fact she's honest with herself. She doesn't buy into the propaganda, nor does she put herself on a pedestal. She knows what she's capable of doing and what her weaknesses are, planning accordingly. That coupled with her calm attitude allows her to look at things with a clear mind. She's second to only Zeke as far as being a tactician and was the most talented of the warriors at collecting information.
1 Zeke's Intelligence Is Unmatched In Attack On Titan's Universe
Zeke's entire character is built on how intelligent he is, putting a vast distance between him and the closest person to him in intelligence in Attack on Titan. He was able to deduce that despite being captured, Annie wasn't being tortured, thus gaining the Founding Titan was of greater importance. His tactics in battle were second to none, always making maneuvers that would ensure he came closer to his goals, no matter the lives at risk.