The belief among Attack on Titan fans is that Eren Yeager's shift to a villainous role in the series finale was too sudden and unjustified. However, this perception may not be entirely accurate. Throughout the series, Eren is depicted as a victim of tragic circumstances beyond his control, which ultimately shape his final choices.
At a young age, Eren is forced to take a life in order to save Mikasa from kidnappers. Shortly thereafter, Titans attack, and he witnesses the horrifying death of his mother at the hands of a Titan - who he later discovers to be his father's first wife in Marley. This traumatic event fuels Eren's deep hatred for Titans and his unwavering determination to eradicate them. However, his father eventually injects him with the Titan serum, unknowingly forcing Eren to consume him and inherit his memories. It is only much later that these hidden memories resurface.
As a member of the Survey Corps, Eren becomes an outspoken advocate against the Titans, unaware of his own tragic connection to them. His perspective drastically changes when he discovers that his friends, Bertholdt and Reiner, were actually working for Marley and were the Titans responsible for breaching the wall, ultimately leading to his mother's death.
Eren Yeager's Turn To Villain Is The Natural Consequence Of His Circumstances
Even the toughest person would be deeply affected by these devastating circumstances. However, Eren, despite his strong exterior, lacks resilience when it comes to his mental state. In his younger years, he often relied on others, particularly Mikasa, to help him persevere. As he gets older, his entire perception of life, from his parents to his belief in the fight against the Titans being a battle for humanity, is shattered, revealing the truth that it is an age-old conflict between neighboring nations. This revelation completely upends Eren's worldview, leading him to realize that no one, not the Eldians, Marlians, or even himself, can claim the moral high ground.
In this new perspective, Eren sees everyone as either a predator or a victim. In such a harsh environment, he chooses the most logical course of action: to protect his people through an absolute interpretation of the "survival of the fittest" principle. However, Eren still appears somewhat troubled by his decision, but there is no one who truly comprehends his unique situation. He indirectly seeks Mikasa's guidance by asking her "what he means to her." Some fans believe that if Mikasa had openly declared her love for Eren at that moment, she could have prevented him from becoming a villain. Unfortunately, the lack of clarity in her response only further propels him towards his apocalyptic resolution.
Despite the devastating aftermath of his actions, Eren harbored no remorse or guilt, steadfast in his conviction that these were necessary steps to take, and he alone possessed the means to carry them out. Ultimately, Eren was an ordinary individual, vulnerable and overwhelmed by the circumstances thrust upon him, with no available support to assist in exploring alternative paths that could alleviate the world's animosity towards the Eldians and integrate them into the global community. Hence, while some may view Eren's transformation into a villain in the climactic finale of Attack on Titan as coerced or unjustified, the truth is that it was an inevitable outcome dictated by the circumstances in which Eren found himself.