Eren Yeager's character arc is the most controversial transformation in anime history. He begins as a hot-headed child screaming about killing all Titans, and ends as a man who chooses to flatten 80% of the world's population.
The Turning Point: The Basement. When Eren discovers that humanity exists beyond the walls — and that his people are hated by the entire world — his worldview shatters. The enemy isn't Titans. The enemy is the world itself.
The Quiet Monster. Post-timeskip Eren is unrecognizable. Cold, calculated, and willing to sacrifice his friends for his vision of freedom. The attack on Liberio is the moment he becomes the villain of his own story.
VERDICT: Eren isn't a hero who became a villain. He's a child who was given godlike power and made the most human choice imaginable — he chose to protect the people he loved, even if it meant becoming the devil.