Seven Of Nine, and it's not even close.
Boring, bland character, catsuits and hairdo that for me undid the obvious "sexualisation" they were going for with the character.
If they had put her in a starfleet uniform with her hair down and allowed just a modicum of personality, then maybe it would have worked, but the character just failed on every level for me yet still became a pop culture icon that transcended Trek.
and i still can't figure out why
Hmm...I personally would NEVER describe her as bland or boring. I like her bluntness and sarcasm. Also relearning how to be a human being in and of itself is interesting. I love her interactions with the Doc.
To the people who just like her for her sexy body...young boys...I mean, I just have to say that is NOT why I love her. I love her because she makes me laugh, she's badass, and has some amazingly sarcastic lines.