What's his name? How did he get his powers? Why doesn't he charge for his services? Does he train Pokemon? What Pokemon? Why's he in Kiloude City? Is that where he's from?
Grey, a.k.a The Judge is was a Pokemon trainer from Johto. Throughout his journeys, he traveled through Unova. An rock slide on Twist Mountain left him with a sprained ankle and very little hope of getting to the next town. That is until Anthea, N's foster sister, finds him. Long story short, Grey falls in love with Anthea, Team Plasma and their ideals. In the time spent with them, Grey befriends N who trains him how to talk to Pokemon. Grey never mastered this skill however it became possible for him to see a Pokemon's potential.
Once Ghetsis' true plans became apparent, the top lieutenants of Team Plasma deemed not loyal were quietly killed off one by one. At Anthea's pleading, Grey escapes from the castle but loses his closest friend, Percy the Persian, who stayed behind to prevent his capture. Percy's fate is unknown.
Wanting to remain on the down-low, he travels to another region, Kalos. Never revealing his name or past, he settled down in Kiloude City, considering it was small enough to easily get to know the locals, while large enough to blend in and disappear if need be. He spends his time helping passing trainers assess the potential their Pokemon hold.
Just something I came up with on the fly.
"Tren, forget the men, we gotta beat up Om, Zet, and YD cause they stole <Insert name here> secks hack."