The absence of freedom and personal security takes a toll on everyone, regardless of age. Living with the eternal threat of Titans looming over one's head is bound to make people revert to their survival instincts. Most of the main characters in Attack on Titan are children at the beginning of the story, so their childish behavior doesn't really come as a surprise.
Although some of them are relatively mature as kids, some remain at the same level of naivety even after growing up. In fact, Attack on Titan's protagonist might as well be a poster child for lack of emotional development. That said, there are more than a few characters who can be considered mature, proving that circumstances, dire or otherwise, have a limited influence on personality.
10 Eren Jaeger Allows The World To Burn To Satisfy His Vengeance
Eren is frozen in time, forever reliving the events of the Titan attack that led to his mother's death. His grandstanding has little effect for the most part, given that he's not the only child to lose a family, but acquiring the Attack Titan gives Eren the freedom to exercise his beliefs in a way few other characters can.
While Eren does love his friends, the fact remains that he insists on fulfilling his childish desire to rid the world of Titans, even if it means destroying everything else in the process.
9 Sasha Braus Is Known As The "Potato Girl" For A Reason
Sasha's early childhood was filled with animosity for the people who were displaced by the destruction of Wall Maria, but her close relationship with her Scout pals allows her to emerge from her cocoon of bigotry and develop a certain level of maturity.
That said, Sasha doesn't really care for decorum, as evidenced by her voracious appetite and complete disregard for the rules. The term "Potato Girl" perfectly embodies Sasha's vibrant, albeit naive, personality.
8 Annie Leonhart Puts Up An Instant Barrier When Faced With Problems
Annie's brusque behavior and overly detached character are derived from her experiences as a Marleyan Warrior and her desire to reunite with her father. She's considerably logical when it comes to her missions, explaining why she has access to the Female Titan in the first place.
Unfortunately, Annie's first reaction to seemingly unsolvable conundrums is to cloister herself behind an unbreakable barrier, both emotionally and literally (in the form of Titan crystal).
7 Reiner Braun's Morality Appears To Shift With The Tide
Reiner only obtains his position as the Attack Titan because Marcel convinces the Marleyan authorities that his young brother Porco wouldn't be a suitable shifter. This revelation is followed almost instantly by Marcel's death, pushing Reiner down a spiral of guilt and self-hatred that takes him years to climb out of.
As a result, his actions in Paradis are psychologically inconsistent: Reiner's righteousness appears to shift with the tide, proving that he really doesn't know what he's doing or who he's fighting for.
6 Jean Kirschtein Fights Until The Very End
Although Jean would like everyone to believe that he's a selfish man who wants to be in the Military Police for the money and the security that the job affords, he's genuinely one of the more loyal characters in Attack on Titan.
Jean takes an instant disliking to Eren because the latter's optimistic philosophy grates on his nerves; their hostility even spills over into a brawl. Despite everything, however, Jean remains with the Scouts until the very end, holding Connie as they both wait for the Shining Centipede's gas to transform them into Titans.
5 Levi Ackermann Ensures His Team's Well-Being Every Step Of The Way
Levi's combat finesse is undeniable, as is his flair for leadership. Not only does he personally involve himself in battle, unlike several army superiors who would rather have their subordinates do the dirty work, Levi also ensures his team's well-being every step of the way.
On the other hand, his manic compulsion for cleanliness and generally aloof nature shows that Levi still treats his heart as something to be shielded at all times. Thankfully, he seems to be more at ease with the world three years after the Rumbling.
4 Hange Zoë Allows Anger And Hatred To Pass Through Them
Hange's scientific method, and, by extension, their whole character, might come off as unconventional, but their rational approaches are always tempered with more than a dash of compassion. They regularly check up on their juniors, offer their eccentric counsel freely, and is a pleasure to be around.
Hange is plagued by the same horrors as everyone in Paradis, but they choose not to direct their anger at the Titans, believing that they're merely mindless monsters who shouldn't be held morally accountable for their actions.
3 Mikasa Ackermann Doesn't Brag About Her Many Accomplishments
The murder of Mikasa's parents is a turning point in her life because she meets Eren, a person she would grow to love more than anyone else, often to the point of open bias. Regardless, it is her love for Eren and the need to protect him that pushes Mikasa to greater and greater heights, eventually landing her at the top of her class for the Scouts Regiment.
She doesn't enjoy bragging about her achievements, however; as such, Mikasa prefers to avoid any sort of attention. That being said, Eren occasionally finds her mother-hen-like tendencies to be a bit excessive.
2 Erwin Smith's Intelligence Includes The Logical And The Emotional
The power that Erwin Smith wields is not borne of political intrigue but of trust. As painfully logical as he is, he understands that camaraderie can only exist when all members of a regiment are treated equally.
Emotional intelligence is a big part of Erwin's character, and it drives nearly every decision he ever makes in his life. He is always the first to lead the charge to battle or take a plunge into grimy politics, proving beyond the shadow of a doubt that Erwin Smith's determination is literally unbreakable.
1 Armin Arlert's Empathy Is Radical, Even If He Is The Last To Realize It
Armin is shy, feeble, timid, perhaps even frightened, but he's the only one who beats himself up over his perceived character weaknesses. Mikasa and Eren can see through their friend's facade of meekness, and they greatly appreciate who Armin really is.
It takes a while for Armin to find himself, but having to deal with an unrelenting Eren in the midst of a global genocide takes more patience than any other character in Attack on Titan is capable of. Armin's empathy is radical, even if it is sometimes overshadowed by his so-called negative traits.