Without burying you in a wall of text, a brief synopsis on an old character I loved the backstory to.
Trainer originally from Kanto, runs away to Johto prior to officially becoming a trainer, taking her family's Ninetails with her. Several years later, she takes the title of Johto League Champion and is pulled into helping root out and is quickly roped into hunting down and eliminating (a more dangerous) Team Rocket. Successful in many of her missions essentially ended up painting a target on herself.
Once everything was said and done, she'd been left severely injured, disfigured, and had to bury half of her team. Not being able to defend her title by League standards, she steps down and passes the title to one of her Elite Four.
She's more than likely hanging around Sinnoh snooping through the ruins of Aether's 'haven.' Haven't really thought of a reason to be in Sinnoh yet. *shrugs*
Hmm. Seems like an interesting character. One we could probably find a side plot for. Okay, I'll accept that!