Kixx is a decent experiment. He's made for all-out physical combat, which is both destructive and understandable.
The part where Stitch and Kixx had a showdown would have been better if the colours hadn't been messed up. It made my eyes go weird.
There's also the strange point that Stitch had to be 'trained'. Stitch's physical ability and dexterity, I thought, would have come from instinct, like his natural urge to destroy anything. It seemed a bit odd for them to say that he had to be 'trained'.
Having the rubber of a tennis she and macadamia nut oil combine to form a galactically-known dangerous substance wasn't a bad idea, but I think Jumba was genius enough to protect Stitch from it. Now we find out he didn't.