Well, the waysee it, Sunset is something else.Twilight got her alicorn powers ultimately because she understood how much friendship means to her and the means she would go to keep it. Twilight grew as a person, but it's the bonds she made with her friends that made her eligible for alicornhood.Sunset on the other hand used friendship as a way to keep herself steady while she tried to understand herself. When she was ready, she approached herself in a night of contemplation and revelations ('My Past is Not Today')Sunset and her growth is a journey of self exploration and acceptance. She is her own worst enemy.Oh, and I disagree on the whole, 'closed forever', thing. It's very contradictive to the themes that are constant throughout the show, of redemption and forgiveness. Sunset being closed off to alicornhood because the worst thing she did was mind control a school? Well, Twilight mind controlled half the town in, 'Episode Zero'. And when the entire town was in throes of violence and mind control, all Twilight cared about was that Celestia was going to miss the friendship letter of the week.This is a fault of Twilight on the opposite end of the scale that Sunset had. Twilight cares too much of what Celestia thinks, to the point she worries more about her being disappointed in her than the well being of the town she lives in. And Celestia knew this! The whole lesson of the Season 3 opener was for Twilight to forgo a direct order from Celestia for the good of the Empire, to sacrifice her pride for everyone else.People stumble and fall, and Twilight has screwed up plenty. It's about admitting mistakes and trying to do the best you can now.Sunset however was a prodigy unicorn who was so obsessed with becoming the best she could be, she was horrified that the only person (that we know of) she was open to had hid a whole new world of possibilities from her (Princesshood). She was so infuriated at Celestia for rejecting her demands that she abandoned her world to try and take over another just so she could arrive back as a conqueror and show Celestia how wrong she was to doubt her.While both grew in both a personal and social way;Twilight became an Alicorn because of her external relationships and what they mean to her.Sunset became what she is now because of her internal relationship and what she means to herself.