Karai from Teenage Mutant Ninja Turtles 2003.
She's loyal to her evil dad (Shredder) and is no stranger to how ninja clans work - But she tries to be diplomatic at first, does have a sense of honor and seeks the turtles help when her dad crosses the line of threatening the lives of countless innocents.
This is not a weird standard so far - but when the turtles bring the downfall of her dad, she becomes pent up on revenge and tries to kill them all. She was deceived into believing her plan worked and expressed no remorse in response. Leonardo had to threat her life for her to back off.
I've seen comments expecting her to be like Zuko from Avatar (didn't finish that series yet but I know how a few things go), but this isn't Karai. She's more of a "soft villain" rather than a anti-hero or a redeemed villain. Will try to do things the nice way first, but won't shy away from her nature when the time comes.