I don't have an all-time best/worst dressed, but i've recently completed Skip Beat and in that one I'd have to nominate:
Worst dressed - Gong Xi (the female lead). Those who are familiar with this franchise know that she dresses kinda shabby, not to mention the appaling pink jumpsuit. So they made her wear horrible clothes but at least it was intentional.
Best dressed - Sho of course! I mean, Shang. Donghae <3

Visual-kei look <3