Kara for me combined every element, beautiful face, beautiful movement, expressive, dynamic, exciting, equally good in both disciplines, and almost tantamount to a ballerina, especially in the Viennese Waltz. She was almost embarrassingly good. Other ladies like Alesha, Jill, Rachel et al have all been marvelous but for me, just miss one or two of the elements.
Men? I think looking back over the whole shebang, I'm going to have to go with Mark as a non performer somebody who just made an amazing leap from not speaking a word in the first week to taking charge with Bruce on the salsa meltdown, and then to confidently performing that fabulous AT and being so emotional in the Tesspit afterwards. He's still unparallelled for me in male latin, and when you watch back Karen's routines, for the most part, you just see how good her choreo is, how good they are together, and how you didn't need any effects or props to create magic, it was just the two of them on the floor. For me, definitely the most memorable SCD couple.