Okay, my friend: Pterobat, at her blog: Lair of the Pterobat; and another blogger I read, Ian over at Monsters of New York (both great blogs, may I add... read them, subscribe to them), have both been posting quite a bit about Karai in the 2003 "Teenage Mutant Ninja Turtles" series. Specifically, Pterobat discussed how she felt Karai's character arc was mishandled in the series' fifth season, and Ian posted his ow thoughts on that. To say I also believed Karai's arc was mishandled would be an understatement.
Personally, I enjoyed the 2003 "Teenage Mutant Ninja Turtles" series quite a bit. I thought the first four seasons were pretty solid, and the director's cut of "Turtles Forever" is great. I did not like the lost season, and I didn't like "Fast Foward" and "Back to the Sewers" at all. I don't love it like I do other series, it'll never make my Top Ten list or anything, but it was good. As for Karai, I thought she was a great character, even if I don't think the voice actress fit the character... or maybe she received some bad direction.
Karai is the Utrom Shredder's adopted daughter. He took her in off the streets, raised her and brainwashed her to be his most loyal servant. Definitely one of the few who knew his true nature. She was fanatically devoted, and also had a sense of honor... when she grew to respect Leonardo and gave him her word the war between the turtles and the Foot was over, she tried hard to keep them alive when her father resumed command of the Foot. After her father was exiled, she swore vengeance on the turtles and could have become one of TV animation's great female villains alongside greats like Demona and Azula. Sadly, this was all derailed in the fifth season when she was turned into a helpless victim at the hands of the resurrected Tengu Shredder (don't ask), and then fell in love with creepy scientist stalker guy named Dr. Chaplin, who was obsessed with her since season three. Pterobat compared him to Upchuck from "Daria" and she was right to do it.
Ian theorized that this might have happened because the writers didn't know what ending to give her. I never liked this development in Karai's character either. But, after thinking about this for a bit, I think the resurrection of the Tengu Shredder should have been a part of Karai finally crossing the moral event horizon to avenge her "father." Tengu Shredder is partially resurrected by the Foot Mystics, his old host the original Oroku Saki (again, don't ask) isn't viable anymore... it needs a new host. The tengu and Karai make the same deal. History repeats itself, and in the end she is consumed and destroyed by her quest for vengeance. It would have been sad and tragic, but it would have given the character far more dignity than walking off into the sunset (sunrise) with Upchuck.
Aside from the fact that she kinda liked and respected Leonardo, what made Karai a good person? She was still a top ranking member of an international crime syndicate (she was Vicious, and the Shredder was the Van to all you "Cowboy Bebop" fans). There was still blood on her hands. Whether she thought the her "father's" Utrom enemies were monsters or not, she was still harming people who had nothing to do with that conflict. There are so few great female villains in television animation anyway, and here we had the potential for another great one. I thought it was wasted. I only bought her turn in "Turtles Forever" when the fate of all existences was at stake.
I know Karai was the character that walked the line, but when the line is walked, eventually a choice will have to be made. If there are no viable or workable paths to "the good side" and very viable and even creatively superior paths to the "dark side" then the "dark side" is what must be chosen instead of forcing in a happy ending that for various reasons that Pterobat explained well in her blog really doesn't work for both dramatic reasons and for very unfortunate implications.