Who is it? It can be any of the major ones (Bowser, Ganon/Ganondorf, Dedede/Marx/Nightmare/Dark Matter, Andross, Ridley). or a minor one off villain from a game we've never heard of, but who's your favourite?
Dark Link was ok in AoL. I never saw DL in ST because I quit because of spoilers and quiet frankly I don't want to see Dark Link in those crappy graphics. I already have to see a ruined Dark Link in SSBB.
