Wow. This became a lot hard than I originally thought… My mind immediately jumped to one, but I was quickly reminded how really great many of them were!
If I was going for beauty, I’d pick Madeleine Swann.
If I was going for kickass, I’d pick Wai Lin.
But, after going back to my initial pick, her pure maliciousness in manipulating her father, M, Renard, Davidov, and even Bond himself, makes her the most dangerous and prolific of them all. Elektra King has my vote and carries it strong.