Levi is the squad captain of the Special Operations Squad within the Survey Corps, widely recognized as humanity's strongest soldier. He was born in the squalid underground city beneath the walls, the son of a prostitute named Kuchel Ackerman. After his mother died from illness, he was taken in by his uncle Kenny Ackerman, a notorious killer who taught him combat and survival skills before abandoning him. Levi then lived as a thief and criminal until he was captured by Commander Erwin Smith, who offered him and his companions a choice between joining the Survey Corps or facing execution. Levi accepted and quickly distinguished himself as an exceptional soldier, eventually rising to captain and leading an elite squad hand-picked by him.

Levi's personality is marked by a stern, disciplined, and outwardly cold demeanor. He holds himself and others to rigorous standards, tolerating no disorganization or lack of commitment. He has a pronounced obsession with cleanliness, which serves as a coping mechanism for exerting control in a chaotic and violent world. Despite his emotional restraint, he possesses a strong sense of morality and empathy, showing deep care for his subordinates and a fierce protective instinct. He rarely expresses feelings openly, but his actions are consistently guided by loyalty and a desire to honor the sacrifices of those who have fallen.

Levi's primary motivation is to fulfill the promises he made to his fallen comrades, particularly to Erwin Smith, and to ensure that their deaths were not meaningless. He carries the weight of humanity's hope and his own losses, driving him to fight relentlessly against the Titans and later against other threats. He does not fight for personal glory but out of a sense of duty and a commitment to the cause of freedom.

Within the story, Levi serves as a protector and commander, especially for Eren Yeager, whom he is tasked with guarding and, if necessary, executing. He leads his squad in dangerous missions and plays a pivotal role in major battles, often turning the tide with his unmatched combat abilities. His role extends beyond mere fighting as he also provides strategic direction and moral authority within the Survey Corps.

Key relationships include his deep loyalty to Erwin Smith, whom he admires unreservedly and whose orders he follows without hesitation. He has a complex bond with his uncle Kenny Ackerman, marked by abandonment and a later reckoning that helps Levi understand his own past. He holds a strained but ultimately trusting relationship with Eren, and he respects Mikasa Ackerman as a fellow warrior of the Ackerman bloodline. He values Armin Arlert for his tactical brilliance. The loss of his original squad members Isabel and Furlan in his early days with the Corps is a formative trauma that shapes his resolve.

Over the course of the series, Levi's development is marked by the accumulation of losses and his struggle to continue fighting despite them. He grows from a hardened survivor into a leader who places trust in his comrades and learns to make impossible choices. His defining moment involves deciding to save Armin rather than Erwin, choosing to let his commander rest and entrusting the future to the next generation. Even after being gravely wounded, he persists in his mission, ultimately fulfilling his vow to kill the Beast Titan.

Levi's abilities are extraordinary. He is considered the most formidable soldier alive, possessing superhuman strength, speed, and reflexes. He is a master of the omni-directional mobility gear, performing maneuvers that no other soldier can replicate. His combat style is brutal, precise, and devastatingly fast, allowing him to defeat multiple Titans in rapid succession. He is also a skilled hand-to-hand fighter, trained by Kenny, and possesses sharp tactical intelligence, enabling him to read battlefields instantly and make split-second decisions. His abilities are partly attributed to the Ackerman bloodline, which grants him heightened physical capabilities and combat instincts.