I get tired of the whole 'FFF-class' label sometimes. The evolution almost always follows the same beats: they start out getting dunked on by everyone, then they stumble into some absurdly powerful cheat skill or hidden potential, and suddenly they're the one doing the dunking. The interesting part isn't the power-up itself, but the personality shift. A truly good story makes you believe the character's internal change.
Take 'Solo Leveling'. Sung Jin-Woo's physical transformation is cool, but it's the quiet erosion of his former meekness that sticks with me. He doesn't become a generic badass; he becomes someone profoundly isolated by his power, which adds a layer of melancholy to all the action. The best evolution isn't just about getting strong enough to win fights, it's about the fight changing who you are at the core. The action scenes are just the flashy proof of that internal cost.
Other stories, though, just use it as pure wish-fulfillment fuel, and I can't blame anyone for enjoying that. Sometimes you just want to see the underdog stomp.