Fluttershy.

Fluttershy was born in Cloudsdale. Her father was a neo-nazi that died in a rally to turn Cloudsdale into the Fourth Reich. This left her with her mother, a ground loving hippy.

She grew up in the sketchier parts of Cloudsdale and her mother was often shot at but used the powers of the trees to block the bullets. Her mother is actually Celestia and she has two brothers. One of them is evil and broke the seconds horn. Also they can go to Toontown randomly because why not.

Fluttershy started flight school at age 65. She was promptly kicked out after they realized she was an earth pony with wings glued to her. Disheartened, she stayed on a cloud.

While chasing after a pony to violently take her rage out on, she fell. And we all know what happens after that.