From Bulbapedia, the community-driven Pokémon encyclopedia.
J (Japanese: ポケモンハンターJ Pokémon Hunter J) is a Pokémon Hunter who, with the help from her henchmen, steals trainers' Pokémon and sells the Pokémon requested by her clients for a profit. She first appeared in Mutiny in the Bounty. Her Japanese voice actress is 本田貴子 Takako Honda and her English voice actress is Sonny Dey.
In the anime
Using a special bracelet, she can turn Pokémon into stone before they can fight back and imprison them in jars.
In Mutiny in the Bounty, she first stole Melodi's Gardevoir. Thinking Ash's Pikachu and Team Rocket's Meowth would be worth a lot, she stole them, too, thus forcing Ash to join forces with Jessie and James to rescue them. Following a brief confrontation with J, they managed to sneak into J's airborne base and rescue their Pokémon and all others she had stolen, before returning them to their rightful trainers. Though several of her henchmen have been captured by Officer Jenny, J remains still at large. Jessie, James and Meowth especially seem to harbor a grudge against her ever since she Pokénapped Meowth.
In A Secret Sphere of Influence, the Eterna City Officer Jenny guessed that J commissioned Team Rocket to steal the Adament Orb, but the the people responsible were Team Galactic.
J appeared again in Ill-Will Hunting!. This time, she was on a mission to steal a group of Shieldon, but was foiled by Ash and his friends, with the help from Gary Oak. Her employer cut off the deal to obtain a Shieldon when Officer Jenny is near. After telling Ash and Co. not to get in her way next time, she tells her second in command to establish radio contact with their employer that they will not be doing any service with him again.
This listing is of J's Pokémon as of Ill-Will Hunting!:
J has a bracelet that shoots out a beam of light directly to a Pokémon. The Pokémon then glows white and is turned into gold. When they're gold, J puts them into special cages that have the ability to control how covered in gold a Pokémon is.
Her goggles also have many abilities, like predicting where a Pokémon using Teleport will appear.
She also has six-wheeled cars driven by her henchmen that can shoot out nets and have retractable arms.
She also travels through the Pokémon world in an airship, which also serves as her hideout.