Constant breakouts don't necessarily result in acne scars. It depends on what type of skin you have and how inflamed the skin becomes. Example: there are just as many Afro-Carribean people who get severe acne, but they don't often scar. Why? Their skin is more resilient to the elements, such as the heat, so it's more resilient to blemishes.
I remember Kim broke out in spots fairly badly a few years ago, but since then it seems to have subsided. And even a few years ago it didn't look dense enough to fully cover her face.
Either way I actually think she looks prettier than she has ever done at the moment. Ricky Martin and Liz Hurley both have acne scars.