Kenny Ackerman (ケニー・アッカーマン Kenī Akkāman?) was a member of the Military Police Brigade's First Interior Squad and the captain (隊長 Taichō?) of the Anti-Personnel Control Squad. An infamous serial killer known for slitting his victim's throats, he was proficient at evasion enough to become an urban legend known as Kenny the Ripper (切り裂きケニー Kirisaki Kenī?). Reiss family had possessed for himself. He was the maternal uncle of Levi Ackerman and had taught the latter as a child on how to survive the Underground. Kenny Ackerman was a very tall and slim man who appeared to be well-built.
He also had a bowler hat with a white band around it.
He had short, coarse-looking dark hair that reached to his neck and also had a thin beard along his jawline. He had the appearance of a middle-aged man with wrinkles around his eyes, which were small and piercing. He was mostly seen wearing a simple white shirt with a black tie that was never fully done up, and a large black overcoat that reached past his knees. He also had a bowler hat with a white band around it. He was almost always seen wearing a pronounced scowl, even when making a foul joke. When not engaged in combat, Kenny, like his fellow Military Police, also fashioned a black trench coat, along with his standard attire and bowler hat. When he was younger, Kenny had a more defined face and much fewer wrinkles. He did not have a beard but he still had dark sideburns. Also, his hair seemed to be slightly longer. He used to wear a long coat, dark trousers and shoes, a white button shirt and another hat. Kenny wanted power, and his personality was molded around this goal. He operated with utter professionalism, hiding his emotions behind a fixed expression and showing neither remorse nor pleasure in his mission. He also showed a strong impulse to kill Uri Reiss when they first met. Kenny expressed a desire to live a "fun" life, but had a strange idea of what he considered "fun," commenting that he believed his grandfather's story about the Ackerman clan's history because it would be more fun to do so, and commenting that growing old and living a full life did not sound fun.
Eren Yeager in order for him to fight against Historia just for his own entertainment, even though the future of humanity was at stake. He had shown a cynical mood occasionally, like when he told Rod Reiss that he was sticking around because he was looking for a toilet. Even so, he was able to show true admiration and respect to those who he believed deserved it, like Uri or his second in command. Levi following his sister's passing. This care for others could also be seen briefly in his interactions with Historia in the Reiss Chapel, becoming noticeably saddened to see Historia's slavish devotion to her father's will, despite the consequences that she would face if she followed through with is plan to inherit the Founding Titans. This is not to say he was overly caring; he despised cowards and did not respect them, and cared even less for titles, not hesitating to threaten Rod Reiss, the king of the Walls. Kenny later revealed that he only obeyed Rod as a plan to obtain power, and that his true intentions were always to become a Titan and gain the Founding Titan himself, which was in direct opposition with Rod's goals. After witnessing Uri and later Frieda Reiss become benevolent people after inheriting the Founding Titan, he wondered if the same thing would happen to him too. He wanted to know what does it feel like to be kind and compassionate.
His grand dream was to take the Founding Titan and see the world like Uri once did. Despite his outward confidence, Kenny seemed to suffer from some degree of self-loathing, going so far as to describe himself as "garbage." His poor view of himself seemed to stem largely from a dissatisfaction with his own lack of empathy towards the lives of others, as his entire quest for power was motivated by a hope that gaining more power would make him a more compassionate person like Uri. His self-deprecating nature also manifested itself in a lack of self-confidence, demonstrated by his decision to abandon Levi when the latter was still a child because of his belief that he was not fit to be someone's parent. In the decades prior to the fall of Wall Maria, Kenny was an infamous serial killer that stalked victims in Mitras. His preferred method of killing was to slit the throats of his victims, which earned him his infamous handle "Kenny the Ripper" (切り裂きケニー Kirisaki Kenī? ), and it was rumored that he murdered over 100 members of the Military Police Brigade. During this period, he had a conversation with his grandfather, who was about to die. Kenny informed him that he had murdered more members of the Military Police, and that he also has found his sister, Kuchel, working as a prostitute in the Underground and pregnant. He also explained that one part of the family had moved to the south, over Shiganshina District, but they were still poor.
Then Kenny asked his grandfather why the Ackermans, a bloodline of warriors once close to the crown, were being persecuted to the point of near extinction. His grandfather explained that the Ackermans were not hated, but feared; because their memories, along with those of the Asian races, could not be wiped out by the power of the king who created the Walls. The Ackermans of the past did not tell their children the truth in order to protect them, though this did not stop the persecution. Even so, Kenny found the story funny. Sometime after that conversation, Kenny talked with a contact in the government, who informed him of the existence of the Reiss family, the true royal family within the Walls. Kenny tracked down Uri and Rod Reiss and tried to kill them, but failed when Uri partially transformed into a Titan and trapped him in his hand. Though Rod tried to shoot Kenny while he was immobilized, Uri stopped him, wanting to interrogate him to discover the identity of his contact; finding Kenny's hatred towards them justified due to the persecution that the Ackermans suffered at the hands of the monarchy. Kenny attempted another attack by throwing his knife at Uri, though the latter stopped it with his arm.
Seeing this, Kenny started screaming at Uri, asking for another chance to prepare a proper ambush. To Kenny's shock, Uri released him, and even bowed before him, apologizing for the persecution towards the Ackermans and pleading him to spare his life. Kenny was surprised to see this coming from a king with that much power, and offered to help Uri, which the latter accepted. Kenny became Uri's bodyguard and close friend, and remained at his side until the latter's death. After some years, he returned to the Underground to see his sister but found that she was already dead. He found, and then adopted, her son Levi but introduced himself to Levi as a close friend of Kuchel's, without revealing their true family relationship. Kenny lived with Levi and trained him until he was strong enough to survive for himself; at this point, Kenny abandoned his nephew without saying goodbye. Years later, Uri explained that he would not be long for the world and he would be passing his powers to one of Rod's children, but that he would live on in their memories.
Uri told him that he saw the world as ending in some time but before it happened, he wanted to make a paradise for mankind. Kenny apparently did not witness his friend's death, because in Rod's flashback, he was not present. After Uri passed the Founding Titan to his niece Frieda and died as a result, Kenny made a plan to obtain the same Titan powers Uri had and used his influence to establish the Anti-Personnel Control Squad. It is implied that by this point he no longer was a serial killer, as he referred to it in the past tense to his subordinates; Kenny especially mentioned how the terror that he once inspired dwindled into nothing more than an urban legend. However, the soldiers did not care because, as Traute Caven said, they had given up in the task of killing Titans, and the only remaining alternative is killing humans.
This greatly pleased Kenny, as he had found his new favorite soldier and second in command. In the year 845, days after the fall of Wall Maria, Kenny arrives with a group of soldiers at Historia Reiss's home. He grabs Historia's mother and asks Rod Reiss if she and Historia are related to him. Rod Reiss denies it and Kenny slits Alma's throat. He approaches Historia to kill her too, but Rod Reiss orders him to stop and saves her life, giving her the new name "Krista Lenz" to live by. At one point, Kenny finds himself being stalked by a mysterious girl. Upon confronting her, the girl claims to be an illegitimate daughter he has fostered. Kenny easily sees through her lie, confident he has never done anything that would result in an illegitimate child; before he can apprehend her, however, the girl attacks him and flees into the sewers. Kenny's squad is sent to retrieve Eren and Historia from Dimo Reeves. As his soldiers secure the two, Kenny takes Reeves to a remote spot to speak with him. Leading Reeves into the woods, he tells Reeves that he personally trained Levi and promptly kills the man for betraying the government. After confirming that everyone from Reeves corporation is dead, he tells Caven to prepare the anti-personnel vertical maneuvering equipment. Kenny travels with his two captives to Trost, with Levi and the Survey Corps in pursuit. When Levi attempts to observe Kenny's group, Kenny flanks Levi and his companions and attacks them.
He kills one of Levi's companions but Levi himself manages to escape. Kenny's squad pursues Levi, forcing him to take shelter in a nearby tavern. Kenny follows Levi into the tavern, but is not able to find him. Concluding that Levi is not there, he is caught off guard when Levi begins to talk to him from under the counter. Levi expresses amazement at Kenny's working with the Military Police, and Kenny brushes Levi off by saying that a brat cannot understand adult matters. Kenny continues to taunt Levi, criticizing his decision to join the Survey Corps, and throwing chairs over the bar to antagonize him. As he tries to get closer to Levi, Levi shoots him with the tavern owner's gun. Kenny manages to block the bullet with a chair, saving his life, but is knocked out of the tavern by the force of the impact. As Levi makes his escape, Caven comes to check on Kenny.