The fundamental tension in isekai isn't how much power a character possesses, but whether that power serves their identity or masks it. Megumin represents a radical rejection of the genre's drive toward optimization. By locking herself into a YPS-3 ceiling through a singular, devastating spell, she transforms her magic from a tool of survival into a manifesto of personal obsession. Her lack of versatility is not a flaw; it is her primary source of agency. She chooses to be a glass cannon because the aesthetic of the explosion is more valuable to her than the utility of victory. Conversely, Rudeus operates at a YPS-4 level not through obsession, but through a desperate need for security. His magical prowess is a shield constructed to protect him from the ghost of his former, pathetic self. While Megumin finds freedom in her self-imposed restriction, Rudeus uses his versatility to avoid being broken again. His growth is a process of integration, using his power to anchor himself to a world he feels he does not deserve. This comparison breaks down when analyzing their Power scores because the numbers measure two different psychological drivers. For Megumin, destructive output is a curated art form; for Rudeus, it is a survival mechanism. One chooses a narrow path to define who she is, while the other builds a wide path to escape who he was. The gap between a city-level specialist and a nation-level general reveals that magical potency is often inversely proportional to psychological stability.