Experiment 629 - "Jinx"
Primary Function: 100% Loyal Warrior of Mass Destruction
As far as Jumba is concerned, experiment 629 is a complete failure. He programed it to be completely loyal to him (not to mention it was supposed to be male, he has no idea how he screwed THAT one up), but it became immediately apparent to him that it was not.
After charging experiment 629 with his new geothermal energy generator, she burst out of the holding capsule (first appearing in her "evil form") and proceeded to tear up his new lab. Stitch dashed into save the day, but unfortunately for him, 629 was programmed to be more powerful than him (naturally, like 627 was). After an amazing battle, with a little luck and a lot of creativity, Stitch finally manages to knock her out.
As he goes to make sure she's REALLY KO'd, she wakes up as an entirely new experiment. Dubbed her "good form" for descriptive purposes, she's smaller and much more fluffy, not to mention a total wuss. Stitch growls at her and she freaks out, hiding behind her hands in fear (which freaks HIM out, since she was just trying to kill him moments earlier).
629 has no memory of her actions in her evil form, and it's unknown what triggers the transformation. While she's in her good form, she's shy and docile, never displaying any of the destructive powers she's supposed to have. She rarely smiles and hides her face with her hands or ears when she's nervous or afraid. It's very, very easy to upset her.
In her evil form, she's ruthless and indiscriminate, as if she's an entirely different person. She has many powers, and her ears and hair fan out around her as she levitates. If she has one weakness, it's the fact that she is not Stitch (who's the hero, and the hero always wins in the end, of course).
I fear I've made her too cute. I don't want to make a Mary Sue, but she really, really sounds like one. I assure you that, though very impressive, she's only an experiment-of-the-episode and will be put in her proper place by the time the story is over. And she doesn't have a love interest. That's always a start.