Throughout AoT, Eren was often the one who'd risk himself to help innocent people — he saved Mikasa's life, who at that time was a stranger to him. He would also go out of his way to protect Armin against bullies and always risked his own life to protect others.
For a boy like that to voluntarily murder billions of people... that's a radical transformation. And you can't help but wonder:
Though he started as a young boy who saw the world as black or white, the harsh realities of a Titan-infested world would make him believe that humanity was inherently flawed.
This new perspective and his aching desire for freedom would make him take drastic steps. Besides, losing his comrades and friends convinced Eren that though cruel, his actions were justified and would ultimately save the day. The following reasons also played an important part in his character change.
1. Eren's Mother is Killed In Front Of Him
During the Fall of Shiganshina arc, Eren helplessly watched his mother being eaten alive by a Titan. As he and his friends were being evacuated from the city, he realized that he'd never be able to return home. The bitter truth of this would make him vow to destroy all Titans.
To everyone's surprise, upon learning of Eren's mother's death, his father injected him with the Titan spinal fluid, turning Eren into a Titan. Eren instinctively ate his father and ended up inheriting both the Attack and Founding Titans.
However, this didn't change Eren's hatred for the Titan race. For years, he trained hard to become a soldier capable of fighting Titans.
Why Do Titans Eat People in Attack on Titan?
Why Do Titans Eat People in Attack on Titan? Titans eat humans because of a subconscious wish to regain their humanity.
2. Learning The Truth About The World
Sometime later, Eren discovered that the Titans who attacked Eldians inside the walls were sent by the Marley — people of his own ethnicity.
Eren also learned how the Marleyan commoners were brainwashed to believe that the people behind the walls were demons and how that propaganda had spread to the entire world.
Sooner or later, he realized, the entire world would join forces to attack Paradis. He told everyone that Paradis's best course of action was to strike first before anyone could harm them. But when everyone refused, Eren took matters into his own hand.
Eren Finally Becomes A Villain
To protect his people against Marley, Eren infiltrated Liberio and unleashed his Titan form. He ate Willy Tybur, the Eldian noble who proclaimed war against Paradis, and gained the War Hammer Titan. Eren then brutally massacred hundreds of innocent civilians, making this his first true act of crime. It was a downhill spiral from here.
By this point, Eren had lost all hope for those civilians. To him, they'd been brainwashed beyond saving, and there wasn't any salvation that he could grant them.
1. Making An Enemy Of His Friends
The Survey Corps hadn't approved Eren's attack on Liberio. He acted without informing anyone of his true intentions, leaving his friends angry and confused. Eren went one step ahead and hurt his friends, making them all despise him.
He met with Armin and Mikasa after the attack on Liberio and started accusing Armin of being influenced by Bertolt's memories. When Mikasa tried to defend Armin, Eren told her that he hated her the most and that he'd always been disgusted by her. He said he loathed people who mindlessly followed orders and called Mikasa a slave.
Infuriated, Armin jumped at Eren, but his point was proven when Mikasa instinctively slammed Armin against the table. Eren then brutally beat Armin up, who retaliated by calling Eren "the real slave."
By the end of this, Eren had managed to make his friends hate his guts. And it was all part of the plan.
Why is the Ackerman Family so Strong? - Their Special Power!
Why Mikasa and Levi of the Ackerman family are so strong? As a result of the experiments with Titan Science and Ymir, the Ackermans possess the Power of the Titans as humans.
2. Making An Enemy Of The World
Eren turned the entire world against him when he unleashed the Wall Titans and activated The Great Rumbling. This catalytic event killed 80% of humanity under millions of stampeding Colossal Titans, and the entire world saw Eren Yaeger as an evil villain slaughtering innocent lives.
All the nations in the world, including Paradis, united against Eren. But their combined forces couldn't stand the overwhelming strength of the Colossal Titans.
Eren claimed that humanity was no longer fit to be kept alive. He said he'd destroy every human in existence and free the planet of both humans and Titans alike.
However, when the Titans were approaching Marley's coast, Eren revealed his true intentions to his friends.
What Is Rumbling in Attack on Titan? How Is It Activated?
For centuries, the island of Paradis was protected by walls made of hardened Colossal Titans. In a world that was making constant technological advancements, these Titans were Eldia's last card against those who would wish to see it destroyed. When the Eldian people were moved to Paradis, King Karl Fritz ...
3. Why did Eren become the bad guy?
In the series finale, Eren admitted that he became a threat to the world so that the Survey Corps can kill him and become humanity's heroes. He also said that killing him would end the Power of Titans forever and bring back the humans transformed into Pure Titans.
He wanted the Survey Corps to become heroes so that the rest of the world would no longer hate Paradis. He hoped that it would give his people the chance to build good relations with other countries, and change the narrative that Paradisians were "devils."
By ending the Power of Titans, Eren ensured that the world would never again misuse Titan powers for war or conquest.
His methods might have been wrong, but ultimately, Eren realized that nothing unites humans like a common enemy. He killed billions of people, but ultimately, he freed Ymir from her curse, saved all those humans who were wrongfully turned into Pure Titans, and gave humanity a new start.
Attack on Titan Ending Chapter 139 Explained!
Attack on Titan, a series that continued for 11 years has ended. After Mikasa kills Eren, the world becomes a world without Titans.