(...Longpost is long :D?)
Nickname: Solaf
Species: Zubat
Gender: Male
Reason: When evolved, made an unfortunate habit of sucking the blood of just about anything he could reach
Area: Caves
Background: Solaf used to not be named, just called by his species, by the way.
Anyways, he used to belong to a Trainer, but was never used. While all his other Pokemon grew strong and evolved, he was only brought out occasionally to take up a turn during which he could heal or revive his other Pokemon, mainly his starter, a Feraligatr (he lived in Jhoto).
When his Trainer defeated the Elite Four, his main goal became to complete his Pokedex. As a result, Solaf evolved into a Golbat. He had never had much time to learn kindness, seeing as he had only ever been outside of his ball in battle and when he was very young, so the power went to his head and he began to accquire a taste for blood, starting with his opponent, then his Trainer.
The Trainer wasn't permanantly injured, but Solaf took away his Poke Ball and destroyed it, leaving him wild and bloodthirsty. Eventually, the problem got out of hand when a few Pokemon and maybe a couple of humans died of too much blood loss, and Ezra bothered to travel long-distance to Kanto, where Solaf had ended up, and shot him with a liquid-dart-thing, turning him back into a Zubat.
The loss of power and size turned him subtle again, but he still sometimes sneaks up on sleeping Pokemon and drinks their blood when he can't help himself. Ezra and Rex are currently trying to train him not to do this before he evolves again and goes on another rampage.
Nickname: Scissors
Species: Scizor
Gender Female
Reason: Attacks and kills others for relatively no reason
Area: Plains
Background: Scissors was unwanted by her parents, and was abandoned when she was young. The lone Scyther was left to defend for herself, and grew used to being completely alone, beside some prey and other Pokemon running around.
She was caught later by some workers for the Kantonian Safari Zone, and released onto a grassy field, much like where she lived for most of her youth. She was calm at first, thinking she had merely been shut in a dark place for some reason and then let back out on another spot at home, but spooked when she saw a Gyarados in the water, which hadn't been native to her home. She swiped her arm at the Gyarados' head, which was scouting and above the surface, enraging it and causing it to attack back.
Both were put in critical condition at a nearby Pokemon Center; she had been attacked with multiple Water attacks and a Hyper Beam near the end, and the Gyarados with multiple cuts. Fortunately, both survived (not like they were almost dead anyway) and went back to the Safari Zone a few weeks later.
She stayed secluded for about a month until a rather adventurous female Trainer managed to catch her. She was instantly evolved along with a Poliwhirl that had also been caught.
After a while in her ball, she was sent out with the rest of the team for an introduction. She took an instant liking to the Politoed who had been evolved with her, and they became best friends.
However, the Politoed was traded away after a while. Scissors was devastated, and nearly killed the next Pokemon she was sent out into battle with. Her frightened Trainer released her, leaving her free to attack more Pokemon. She was sad but otherwise okay for a while, until she came across the Politoed's dead body, beaten to death by its new Trainer.
Enraged, she tracked him down and killed him brutally, starting her killing spree. She was chased after by someone working for the Rehab Center, but her fast reflexes made her hard to catch, and the terror ensued for about two months, during which several people died, mostly those who had a Politoed.
She was caught and brought to the Center recently, where Ezra is considering shooting her with a dart. He is unsure, since Scyther still has weapons on its arms, and the memory is probably enough to stay with her through devolution.