Attack On Titan is coming to an end soon and anything can happen. In recent chapters, Eren's plan for saving Paradis and destroying the rest of the world has become a reality. He used his powers to unharden the walls, causing hundreds of Colossal titans to destroy everything in their sights.
A lot of the main characters throughout the series have joined forces in order to stop Eren. However, as readers get closer to the end of the series, it seems that the only way to stop Eren may be to kill him. But who will deliver the final blow?
10 Should: Ymir
Despite only appearing in the series a few times, Ymir has played one of the most important roles. Without her, the nine titans would not have been created and the war between Marley and Eldia would never occur. She has been a slave throughout her life, as well as death. Perhaps her 2,000 years of slavery will end by defeating a monster as powerful as the devil she once made a deal with. After all, she is one of the most mysterious characters in the franchise and could be the key to killing Eren.
9 Shouldn't: Historia
Historia, Ymir's descendant, is the queen of Paradis. Prior to defeating her father and claiming the crown as her own, she was a member of the Survey Corps. She had a lot of interactions with Eren before ruling her kingdom and the two of them became close friends. Though she has proven to be one of the strongest characters in the series, she has not appeared for a while. It is highly doubtful that she would abandon her people and catch up to Eren. Plus, it wouldn't be smart to do so with a baby on the way. However, according to one fan theory, she will name her child "Ymir," who will end up making a deal with Eren, causing a time loop.
8 Should: Reiner
Reiner and Eren have had a very complicated relationship throughout the years. Eren once looked up to Reiner and they considered each other to be good friends. However, when Reiner revealed that he was the Armored Titan, they became enemies and have had many epic battles since. Despite their hatred, they have come to understand each other and realize how similar they are.
Reiner has been one of the most important characters since the beginning and is the creator's favorite character. It would make sense for him to write Reiner as the hero of the story and to have him be the hero that defeats their world's biggest threat.
7 Shouldn't: Annie
Annie was the first main antagonist of the series and became one of Eren's greatest enemies. However, readers learned in the most recent chapters that she doesn't really care to fight and doesn't see purpose in anything anymore. She decided to leave the others and try to protect Gabi & Falco. However, due to how close Eren and the Colossal Titans were to Annie the last time she was shown, she could already be dead. Readers may not see the Female Titan again.
6 Should: Zeke
Eren's brother, the Beast Titan, has the complete opposite mindset of Eren's. While Eren wants to save Paradis and kill everyone in the other countries, Zeke wanted the Eldians to die so that they wouldn't be abused anymore and for the rest of the world to not fear them. As Eren's reckoning is the last thing Zeke would want, he may finally defeat the family that betrayed him. It is also unknown where he currently is as he has not appeared in the past few chapters. Perhaps he'll return and readers can find out what he has been up.
5 Shouldn't: Connie
Though he has been one of the main characters from the beginning and is part of the group trying to stop Eren, Connie has never been much of a fighter. Up until Sasha's death, he was a comedic relief character. Though it would be cool to see him prove that he is better than everyone said he was, he probably wouldn't even be able to kill one of the Colossal Titans. If there is a battle between him and Eren, he would be much better on the side lines, supporting characters like Reiner, Zeke, and...
4 Should: Mikasa
Though a lot of fans ship the two of them, Eren and Mikasa probably will not end up together. He asked her if she had feelings for him and she revealed that she truly does see him as the last family member she has. She always cared for Eren more than anything but has also beaten him and put him in his place whenever he does something that he shouldn't. If Mikasa were to even attempt killing him, he would probably realize that he was wrong. However, due to his stubbornness and recklessness, Eren may not stop even if he regrets his actions, which could cause Mikasa to be forced to kill the boy she calls her brother.
3 Shouldn't: Jean
Eren and Jean have been fighting and arguing since the day they meet. They were each other's greatest rivals in their trainee days and when Eren revealed his titan powers, Jean wanted him to prove that he was worth dying for.
As Jean always wanted the peaceful, quiet life, it was a tough decision for him to join his friends rather than let Eren go through with his goal. Despite hating Eren for a long time, it would be anticlimactic for him to be the one to save what remains of their world.
2 Should: Levi
Eren looked up to Levi ever since he was a kid and was happy to join his team when they formally met. However, Levi has always said that if Eren ever acts without permission and proves to be an enemy to humanity, he would be the one to kill him. It has been foreshadowed all along that Levi would bring an end to his pupil, and in doing so, Levi could also avenge all of his comrades that died at the mouths of titans by ending the most powerful of them all.
1 Shouldn't: Armin
Armin and Eren were best friends when the series began and shared each other's dream in seeing the ocean, along with any other parts of the world they had only read about. They were by each other's side until they finally accomplished that goal. From there, Eren became his enemy and has even attacked Armin.
Though the newest commander of the Survey Corps doesn't feel the same as he once did towards his former best friend, he probably wouldn't kill him. Armin has never been as physically strong as his friends and has always been the strategist in the group. If he were to try and kill Eren, he'd most likely die despite being the true Colossal Titan. As the narrator of the series, he is the character that is most guaranteed survival.