Hunter J

Hunter J frequently referred to as either Pokémon Hunter J, J, or Jay in certain dubs, is one of the main antagonists in anime; Pokémon Diamond and Pearl. She 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, by any means necessary, including abandoning her henchmen, or even killing anyone who gets in her way.

Meeting Ash and Friends
Hunter J first appeared when she attempted to steal a Gardevoir owned by a girl named Melodi. Thinking Ash's Pikachu and Team Rocket's Meowth would be worth a sizable amount of money, so she decided to steal both them. This caused Ash to join forces with Team Rocket to rescue the two.

Following a brief confrontation with Hunter J, they managed to sneak into J's airborne base and rescue their Pokémon and all the others she had stolen, before returning them to their rightful Trainers. Though several of her henchmen have been captured by Officer Jenny, Hunter J was able to escape and remained at large. Jessie, James, and Meowth especially seem to harbor a grudge against her ever since she kidnapped Meowth.

Catching Shieldons
Hunter J appeared again. This time, she was on a mission to steal a group of Shieldon, but was foiled by Ash and his friends, with help from his rival; Gary. Her employer cut off the deal to obtain the Shieldon, since Officer Jenny was near. After telling Ash and his friends not to get in her way next time, she told her second-in-command to establish radio contact with their employer, in order to tell him that they would not be doing service with him again.

Catching Aura Sphere Riolu
Hunter J appeared again where she was hired to steal a special Riolu that knew Aura Sphere, for an unknown client. Ash managed to rescue the Riolu, but Hunter Jay managed to escape again.

Catching Regigigas
Later on, Hunter J appeared again and attempted to capture Regigigas at the request of an unknown client. Hunter J traveled to the Snowpoint Temple and forcefully resurrected Regigigas. Despite this, she was unable to capture it, due mostly to the efforts of Brandon and his Pokémon, and she immediately withdrew from the area when her client decided to cancel the deal.

Joining Team Galactic & Demise
J appeared again. This time, she was hired by Team Galactic to catch the legendary Lake Guardian Pokémon; Uxie, Mesprit, and Azelf, and was successful. Although she was succeed in capturing the Lake guardians, her ship was hit by two Future Sight attacks used by Uxie and Mesprit directly before she captured them, which due to her overconfidence, Hunter J had forgotten about the Future Sight Attack. As a result, J's ship crashed into Lake Valor and sank into a whirlpool while she and her crew members were on board. Once the ship was underwater, the protective glass broke and the ship was flooded with water, causing it to explode, J's glasses left floating to the surface. It is currently unknown if J, her Pokémon, or any of her crew survived. However, as she has not made any reappearances since, it's most likely that Hunter J, her Pokémon and her crew are dead.

Personality
Hunter J is a person who is willing to do anything to capture Pokémon for her clients even if it means injuring people or Pokémon, easily revealing her to be ruthless, relentless, and cruel. In fact, in her debut episode, she sacrificed some of her henchmen without hesitation or remorse, further emphasizing her intensely, sociopathic, greedy, and callous nature. She has no honor, decency, or regard for any form of life. The only thing that matters to her is money, nothing else. She is one of the very few characters in the anime who is purely evil. However, she tends to underestimate her opponents when on the verge of victory, which often leads to her defeat and seemingly her final downfall.