Levi Ackerman is a captain in the Survey Corps and the leader of its Special Operations Squad, widely recognized as humanity's strongest soldier. He was born in the underground city beneath the walls to Kuchel Ackerman, a prostitute who died when he was very young. His maternal uncle, Kenny Ackerman, found him after her death and raised him for a time, teaching him combat skills and survival tactics before disappearing and leaving Levi to fend for himself. Levi grew up as a thief in the violent, poverty-stricken underground, where he became a notorious criminal. His life changed when he was captured by Commander Erwin Smith, who offered him and his companions a chance at a surface life in exchange for joining the Survey Corps. After losing his two closest friends, Furlan Church and Isabel Magnolia, in a devastating Titan attack during his first expedition, Levi chose to remain with the Corps and dedicate himself to fighting Titans, honoring the memory of those he lost.

Levi is known for his cold, disciplined, and no-nonsense personality. He maintains a strict, almost militaristic code of conduct, demanding excellence from his subordinates and tolerating no disorganization, tardiness, or lack of commitment. He has a notable obsession with cleanliness, often cleaning his surroundings even in the midst of battle, which Hange Zoe humorously comments on. This habit is understood as a coping mechanism, a way to maintain a sense of order and control in a chaotic and brutal world. Despite his outwardly harsh demeanor, Levi possesses a strong sense of morality and empathy. He rarely shows emotion openly, but his actions reflect deep compassion and loyalty toward his comrades. He values human life highly and takes the weight of his decisions seriously, especially when choosing whom to save or sacrifice. His decisions are often guided by a desire to protect others and to ensure that the sacrifices of his fallen comrades were not in vain.

Levi's primary motivation throughout the story is to fulfill the promises he made to his dead friends and to Erwin Smith, whom he deeply respected. He carries the burden of being humanity's strongest soldier and the hope that comes with that title, but his driving force is not glory or personal ambition. Rather, he fights to give meaning to the lives lost and to protect those who remain. He is acutely aware of his own limitations and does not pretend to have all the answers, often advising others to make choices they will regret the least.

His role in the story is pivotal. As captain of the Special Operations Squad, he takes Eren Yeager under his wing, acting as both his bodyguard and, if necessary, his executioner should Eren lose control. Levi leads dangerous missions, participates in critical battles against the Titans, and makes several high-stakes decisions that shape the course of the narrative. One of the most significant moments is his choice to save Armin Arlert over Erwin Smith, believing that Erwin had already shouldered enough and deserved rest. He later fulfills his promise to Erwin by killing Zeke Yeager, the Beast Titan, in a brutal and decisive confrontation.

Levi's key relationships include his bond with Erwin Smith, who gave him purpose and whose leadership he trusted completely. He respects Mikasa Ackerman's combat prowess and shares a distant bloodline connection with her, though he remains more controlled than she is. He values Armin Arlert for his strategic mind and relies on his tactical judgment. His interactions with Kenny Ackerman, his uncle and former mentor, are fraught with tension, betrayal, and eventual understanding of his own origins. He views Reiner Braun as an enemy and engages him in intense combat, while he acknowledges Pieck Finger's intelligence and strategic value as an opponent. His relationship with Floch Forster is marked by deep ideological conflict, as Levi sees Floch as a dangerous radical.

Over the course of the series, Levi undergoes significant development, though his core personality remains consistent. His journey is one of enduring loss and continuing to fight despite immense personal pain. He starts as a criminal driven by survival, becomes a soldier seeking meaning through Erwin's vision, and eventually evolves into a figure who makes his own choices about whom to save and what to fight for. By the end of the story, even after being severely injured by Zeke's explosion, he recovers and continues to fight, embodying resilience and loyalty.

Levi's notable abilities are exceptional combat skills that earn him the title of humanity's strongest soldier. Despite his short stature, he possesses remarkable strength, extreme agility, and unparalleled mastery of the vertical maneuvering equipment, allowing him to perform maneuvers that seem impossible to other soldiers. He is a highly skilled hand-to-hand combatant, trained by Kenny, and wields his blades with a distinctive reverse-grip technique that enables rapid, spinning attacks. He also possesses a sharp strategic mind, able to read battlefields quickly and make split-second decisions. As an Ackerman, he has access to awakened powers that grant him enhanced fighting instincts and perfect control over his body, allowing him to survive situations that would kill most others.