Levi Ackerman

Short straight black hair styled in a short bob.
Narrow, frightening dull grey eyes with dark circles under them.
A deceptively youthful face.
Levi is of short stature, but his build is well-muscled due to his extensive use of vertical maneuvering equipment.

Captain Levi is described as a "clean freak" by those who know him personally, as Ackerman prefers his surroundings, as well as himself, to be spotlessly clean. He dislikes getting dirty, and has been known to wipe his blood-stained blades while still on the battlefield. However, he will not hesitate to touch dirt if he deems it necessary.
Levi is obsessed with cleanliness.
Despite his penchant for cleanliness, Levi is very aloof and unsociable. He rarely shows emotion, leaving a negative impression on others. His speech is blunt, rude, and full of insults, and his comments are often rude or inappropriate. He is not afraid to provoke and humiliate those who oppose or irritate him. His sense of humor tends toward the vulgar, offensive, and dark. All this makes him very difficult to communicate with for most people.
During his life of crime in the slums, before joining the Survey Corps, Levi refused to obey anyone's orders, though he trusted his comrades deeply. However, after joining, Levi developed a great deal of respect for the Survey Corps' commander-in-chief, Erwin Smith, whose demands and orders he followed without question. Levi also trusts his subordinates.
But Levi's "behavior" only applies to a select group of people he respects. He has no problem displaying open disdain for anyone else, especially those in power. During Eren's trial, Levi openly insulted the merchants, calling them "pigs," and accused the Military Police of incompetence and inability to handle Eren. To ensure Erwin's plan to recruit Yeager into the Survey Corps didn't fail, he had to intervene to prevent Yeager from being shot on the spot.

Levi, on top of that, openly resents the behavior and actions of those in power for their constant attempts to undermine the Survey Corps, presumably due to the criminal life he led before joining the Survey Corps.
Though he rarely displays it, Levi possesses a sense of morality and empathy. He places great importance on preserving human life, urging his squad to use their wits to avoid mistakes that could cost them their lives. This is especially evident when it is revealed that all Titans were once human themselves. The thought that he has been unknowingly killing people all this time deeply troubles him. Levi also took the loss of his original squad at the hands of Annie Leonhart very personally.
Due to his dangerous profession and his own moral compass, Levi cares deeply for the well-being of his subordinates. When ordered to retreat following the fiasco of the 57th mission, Levi was visibly distressed that so many of his soldiers had died in vain. Later, he risked his life in battle with Annie Leonhart, who had previously killed his entire squad, to rescue Eren from her mouth and protect Mikasa, who was blinded by her thirst for vengeance. Upon returning outside the walls, Petra's father approached him and proudly spoke of his daughter and her unwavering devotion to the Survey Corps. Levi remained silent, too overcome by the deaths of his subordinates. He merely said that the will of his comrades lives with him, and that it was this that strengthened his resolve to continue fighting.
Despite being Erwin's subordinate, Levi operates quite independently. Many of his Titan kills were accomplished solo, without direct cooperation from other soldiers. He usually assigns them to patrol the surrounding area. Ackerman gives orders without hesitation when necessary, but doesn't see himself as a leader like Erwin Smith. He doesn't seem to particularly value hierarchy.

Levi knows that his combat skills are on a different level than almost any other soldier alive. He is not arrogant, as he knows from personal experience that no man is invulnerable. Few would argue with his assertions that he alone can handle certain difficult tasks. Ackerman has proven his ability to do so time and again.