I choose to look at it a bit more optimistically. Simon wound up becoming the most powerful being in existence, and he quite literally saved the entire universe from subjugation. And yet, at the end of the day, he had always been Simon the Digger. He played his part, and then he chose to pass it along to future generations to move forward. But he stayed out there, watching over everything, and if there came a point in the future where his power was needed, he'd take up his mantle again.
And as bad as Akame was, Dimension W wins this category head-and-shoulders above the rest. I have never seen moderate potential squandered that spectacularly.