8 Dark Facts About Eren Yeager That Reveal the Dark Side in 'ATTACK ON TITANS', Already Took Lives When He Was Still Young

Eren first killed a human when he was still a child, before joining the military. When Mikasa was kidnapped by a group of criminals, Eren coldly killed them to save her, showing a brutal side and a strong desire to protect the ones he loves from an early age.  

Eren directly influences events in the past using the Founding Titan's power. He manipulates his father, Grisha, to steal the Founding Titan's power from the Reiss family and even influences Grisha's decision to kill that family.

Eren deliberately initiates the Rumbling Plan, which awakens thousands of Colossal Titans to destroy the world outside of Paradis Island. His goal is to eliminate all potential enemies, causing destruction and mass death, including millions of innocent people, to protect his friends on Paradis Island.  

As the story progresses, Eren becomes increasingly fatalistic. He begins to believe that all of his actions are predetermined by fate, and that he has no choice but to follow the path that has been laid out for him, which includes cruel and horrific actions.

At the end of the story, Eren deliberately distances himself from his friends, especially Mikasa and Armin. He chooses not to tell them his true plan, knowing that they would oppose him. This shows Eren's dark side, willing to sacrifice his relationships for a greater purpose.

Eren manipulates Ymir Fritz, the first Titan, to gain the full power of the Founding Titan. He exploits Ymir's trauma and pain to force her to obey his commands, demonstrating that Eren does not hesitate to exploit others, even if they are victims of a tragic history.

Eren realizes that his actions will not only lead to his own death but also to the total destruction of the world he is trying to protect. He understands that even if the Rumbling succeeds, he will be killed by his own friends, and he accepts this fate with despair.

Eren, who initially fought for the freedom of humanity from the Titans, ultimately betrays his original purpose by becoming the greatest threat to humanity itself. This transformation from hero to antagonist reflects the moral degradation that occurs within him as the story progresses.