Attack on Titan has had many plot twists throughout the manga. Some of the best were when the characters revealed things about themselves or made decisions that no one expected, changing the way fans viewed them.
Be it one of the branches of the Paradis army, the Marley Warriors Unit, or any of the other groups in history, fans were shocked when the characters switched sides.
10 Jean was going to join the Military Police, but decided to join the Topography Corps
When Jean first showed up, he wanted to become a soldier in the Military Police. However, once the Titans invaded the Trost district, he realized that his place was in the Inspection Corps. Since the Topography Corps and the Military Police clashed soon after, he could have ended up fighting his former comrades had he joined the Military Police much earlier than necessary. A few years later, the Yeagerists overthrew Paradis, and when Jean tried to stop the Rumor, they considered him a traitor, even those he knew of the 104th Cadet Corps.
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9 Reiner was torn between being a warrior and a soldier
When Reiner was a child, he wanted to become one of Marley’s warriors. However, when this dream came true, she had to do a lot of things she didn’t want to do. During his mission to find the Founding Titan, he joined the 104th Cadet Corps with Annie and Bertholdt, so they fought alongside the people they planned to kill. Like Jean, he originally planned to join the Military Police, but decided to join the Inspection Corps when he learned that Eren was a Titan-shifter. A part of him even began to believe that he was a soldier rather than a warrior. However, he soon after revealed his identity as an Armored Titan, becoming one of the Survey Corps’ greatest enemies until he helped them save the world.
8 Connie was considered a traitor by the Yeagerists
Connie was another soldier in the 104th Cadet Corps who planned to become a member of the Military Police. However, after graduating, he decided to join the Inspection Corps. Considering Reiner a close friend, he was surprised when he revealed his true identity.
A few years later, Connie would also be considered a traitor, as she tried to manipulate the Yeagerists she was friends with before fighting them. He finally understood how Reiner felt.
7 Ymir was a soldier who helped warriors
When Ymir was a child, she lived in Marley. A group of religious Eldians believed her to be Ymir Fritz, but once the Marleyans discovered her, they sent her to Paradis. After inheriting the Titan of the Jaw, he began a new life as a soldier in the 104th Cadet Corps, followed by the Inspection Corps. Due to his past, he was able to understand what Reiner and Bertholdt were going through and betrayed the Survey Corps to help them, allowing Porco to remove the Titan Jaw from him.
6 Kruger was a Marleyan officer, the Owl, and an heir to the Attack Titan
When Kruger was first introduced, he appeared to be an ordinary Marleyan officer. However, he had a secret identity as “The Owl”, the leader of the Eldian restorers. He was also the heir to the Attack Titan and used his powers to kill the Marleyan officers he worked with for years. He then passed the Attack Titan to Grisha, hoping that he could finish his mission.
5 Zeke pretended to be loyal to Marley for years while secretly an Eldian restorer
As the son of Grisha and Dina, Zeke was expected to be an Eldian restorer. However, once Marley was close to discovering who was part of the group, Zeke was forced to betray his parents to save himself and his grandparents. As a result, Marley had a lot of faith in him and gave him the Titan Beast.
For years, he pretended to be a loyal warrior while secretly an Eldian restorer in his own way, believing that by using the Founding Titan to prevent Eldians from being born, he could end the conflict between them and other races. To achieve this, he joined forces with the Study Corps, only to end up betraying them.
4 Levi hated the Surveying Corps at first, but became their strongest soldier
In the spin-off Attack on Titan: No Regrets, it was revealed that Levi originally hated the Survey Corps and joined them in killing Erwin. However, after the death of his two best friends, he became the strongest soldier in mankind. Years later, when the Yeagerists overthrew the Paradis army, he betrayed his nation to stop the Rumbling and save the world.
3 Kenny used to be an assassin before he became the leader of the antipersonnel control squad
Before being introduced, Kenny was the killer known as “Kenny the Ripper”. However, when he met Uri Reiss, he began working with him and ended up becoming the leader of the Antipersonnel Control Squad. The Survey Corps and the Antipersonnel Control Squad ended up fighting each other, causing Kenny to become the enemy of the boy he taught to fight, Levi. In the last moments of his life, Kenny gave Levi the Titan Serum that he planned to use on himself, ultimately helping the Survey Corps.
2 Floch betrayed the Surveying Corps and became a Yeagerist
Floch was a member of the 104th Cadet Corps who originally joined the Garrison, but soon after became a soldier in the Inspection Corps. However, he ended up hating the Paradis military and helped Eren train the Yeagerists to overthrow them. As the second leader of the Yeagerists, Floch became a traitor to his former comrades and ended up fighting them in the hope that Paradis could be saved.
1 Eren became one of the Survey Corps’ greatest enemies and the leader of the Yeagerists
When Eren was a kid, he dreamed of being in the Scouting Corps, wanting to explore the world and kill as many Titans as he could. However, after being able to see the future, it changed dramatically. He betrayed his companions and secretly created the Yeagerists. When he was ready, the Yeagerists overthrew Paradis. Soon after, Eren started the Rumbling, killing thousands of people. However, one of the reasons he did all of this was to have his loved ones from the Survey Corps fight him in front of the whole world and prove they were heroes. In the end, Eren was truly loyal to the Survey Corps despite harming them.