Just the primary ones? Guess I can't include Red Grant or Fiona Volpe, then.
Savalas' Blofeld, Goldfinger, Dr No, Sanchez, Drax, Rosa Klebb, Le Chiffre.
Making this list, it becomes clear to me that a good villain is core to a good Bond film (of course, my own favourite - TLD - breaks that rule, although Koskov isn't bad).
I'm not going to rank the rest of them, as there just comes a point...