The Ackerman clan has been around since the Eldian Empire, originally great warriors to the King. After thousands of years, the once fierce Ackerman clan has withered away, leaving only two members. What happened to this clan of warriors? Would such exceptional people willingly disappear, or was their more devious plans present?
Due to the nature of those within the walls, the truth is hard to find. Perhaps only the holder of the Founding Titan, Eren Jeager, and the few others who have heard the stories will know what happened to the Ackerman clan. Assuming Levi Ackerman and Mikasa Ackerman are anything to go off of, the Ackerman clan is a group of unstoppable warriors. Their skills are unmatched, almost supernatural in nature, much like what fans see when Levi battles the Beast Titan. If all the clan members have such abilities, where did they learn these skills?
Experiments of the King
The skills used by the Ackermans aren't something that can be learned. Instead, this insane power results from experiments done on the subjects of Ymir and the Titans. These experiments gave the Ackerman clan what's referred to as the "awakened power," which is activated when their survival instincts activate. This is why Mikasa didn't display her "awakened power" until after being kidnapped and encouraged to fight by Eren. This is the shift Mikasa felt that day, her power resurfacing.
Since the Ackerman's power gave them an edge over other humans, the Eldian Kings used them as their right hand. Keeping the King protected. For centuries this was the role of the Ackermans, even following King Fritz to Paradis Island to live behind the walls. It wasn't until King Fritz proclaimed his peace mission that the Ackermans opposed the King. The clan of warriors couldn't sit by and allow Marley to kill everyone behind the walls, the idea going against their nature. Perhaps King Fritz could use the Founding Titan to erase the memories of the Eldians and the Ackermans. Preventing any future confrontations that would ensue from the clan.
Exterminate the Ackermans
Sadly, for King Fritz, the Ackermans were immune to the power of the Founding Titan, a result of the experiments thousands of years ago. Instead of humans or Titan shifters, the Ackermans were a group in-between. Fearing the idea that the Ackermans would reveal the secret of the walls, King Fritz ordered their extinction. Forcing the few left in the clan to seek refuge in the underground city and the mountains at the edge of Wall Maria. Following generations kept the secret of the walls in an attempt to keep them safe. By the time Levi was born, all Ackermans were unaware of the outside world and the truth about the walls.
The fear King Fritz had led to only three Ackermans being alive for a time. Kenny Ackerman, Levi Ackerman, and Mikasa Ackerman all changed after Kenny's death in season three and Levi's battle with Zeke. This could mean Mikasa is the only Ackerman alive. As upsetting as this may be, killing off all the Ackermans makes sense in the long run. Before this, the Ackerman were soldiers, not only for the King but for humanity. Levi was considered the strongest soldier, and Mikasa was at the top of her class. The Ackerman clan, in a way, represents the time of the Titans, war, and extinction. With their numbers slowly dying, it could mean an end to an era. Will fans see the death of every Ackerman then?
Unlikely, even with the death of almost the entire clan, Ackermans don't submit to death. Like Mikasa's promise to Eren in season one, Ackerman survive, some for a dream, and others to keep the memories of the dead alive. Mikasa won't allow herself to be killed because this would mean the lives of her fallen friends, family, and Eren will be lost. A brighter alternative is that the Ackerman clan represents humanity's drive to fight back and survive. No matter the circumstances, they'll excel in order to push forward in life.
Mikasa is complimentary to Armin and Eren's characters in relation to the characters. Armin holds the intelligence, guiding the group to victory. Eren is the spirit, keeping the group fighting, even if he has already fallen, and Mikasa is the strength. She can execute and succeed in Armin's plans. Creating a cohesive group amongst the three friends. A similar bond is seen between Commander Erwin Smith and Levi Ackerman. Even with these complementary relationships, both Levi and Mikasa play the roles of supporters to their friends. Sounds similar to what Eren said about Ackerman's following their 'hosts' command. Could this mean Eren was telling the truth, that all Ackerman's are subjected to their power? Fans who have read the manga already know the answer, but those following the anime will have to wait.