The way fans interpret Eren's identity gets at the heart of 'Attack on Titan'. Calling him 'just' a Titan feels like an oversimplification. Over the course of the series, he evolves from a Shifter who could turn into a specific Titan into something far more vast and unsettling. By the end, especially after gaining the Founding Titan's full power and fusing with the Hallucigenia-like creature, he transcends every established category. He becomes the literal source of all Titan life on Paradis, a walking, talking extinction event shaped like a person. The term often used in the fandom, 'The Rumbling' itself, stops being a mere event and starts to feel like his new form—a world-ending entity composed of countless Colossal Titans, moving with a single will.
What makes his identity so compelling in fan spaces isn't just the power scaling, but the philosophical shift. Early on, his Titan form was a tool, a weapon he struggled to master against external enemies. Later, it became the physical manifestation of his own imprisoned ideology and his warped vision of 'freedom'. In the final arcs, he isn't using a Titan power; his very existence is the Titan phenomenon unleashed. Fan art and discussions often grapple with this, depicting him less as a character within a Titan and more as a spectral force, his human body crumbling in paths while his consciousness directs an apocalyptic march.
For me, the most poignant fan interpretations focus on the tragedy of that transformation. He becomes 'something different' precisely because he sacrificed his humanity to pursue an ideal that ultimately required the destruction of humanity beyond the walls. He’s not a hero or a simple villain in a Titan's skin; he’s the physical consequence of a cycle of hatred personified, which is a far more terrifying and fascinating concept. That final conversation with Armin in the paths, where he exists simultaneously as a child, a teenager, and a corpse, cements that he's moved beyond any binary state of being.