Levi Ackerman (リヴァイ・アッカーマン Rivai Akkāman), often formally referred to as Captain Levi (リヴァイ兵長 Rivai Heichō), is the squad captain (兵士長 Heishichō, lit. “leader of the soldiers”) of the Special Operations Squad within the Survey Corps, and is widely known as humanity’s strongest soldier.
Levi is seen leaving Trost District, along with the rest of the Survey Corps, on the 56th Expedition Beyond the Walls—the same day the Colossus Titan attacks the district.
While on the expedition, Levi sees a soldier caught in the jaws of a nearby Titan and kills it. As more Titans approach, Levi orders Petra Ral to take care of the injured soldier while he takes care of the remaining Titans. After clearing the immediate area, Levi checks on the injured soldier, who is quickly succumbing to his injuries. In an attempt to comfort the scout in his dying moments, Levi assures him that he has done his duty well. As the soldier dies, Erwin arrives and informs Levi that they are returning to Trost. Levi is unwilling to turn back so soon, is forced to concede when Erwin informs him that Wall Rose has possibly been breached.
Levi arrives back in Trost in time to find two Titans bearing down on four soldiers at the base of the Wall. He quickly kills the Titans, and demands that the soldiers fill him in on what has happened.
Three days later, after Eren wakes up in the dungeon beneath the courthouse, Levi assures him that the higher-ups will let him join the Survey Corps—and that he himself will make sure Eren does not get out of hand. Should that happen, Levi says, he will not hesitate to end Eren’s life.