I've stumbled across a few fics with that premise, and honestly, most of them get the growth part backwards. They have Harry storming off after a rejection only to become this ultra-powerful, cold lord with a harem, which isn't growth—it's a revenge fantasy. A story that handled it with some nuance, though I'm blanking on the title, had him leaving Britain quietly. The growth came from him realizing his entire identity was tied to being 'The-Boy-Who-Lived-To-Win-Hermione' and having to build a life without that script. He apprenticed in a different magical community, made mistakes with new people, and slowly learned to value connections that weren't forged in a war. The rejection wasn't the catalyst for power, but for a long, awkward period of figuring out who he was when no one expected anything from him.
That fic stuck with me because the 'Hermione rejects him' scene was almost an aside, not a dramatic showdown. The real story was Harry learning that his stubborn pursuit could feel like pressure to someone else, which was a tough but necessary lesson for the character. He didn't come back a god; he came back a quieter, more thoughtful person who could finally see Hermione as a complete human separate from his own story, not as a prize he'd failed to win. The growth was in the quiet moments, not the big battles.