this is actually a tough question (posted in the wrong category mind you). I guess it all depends on how and who you would interpret the consiglieri to be in parts II and III. I would say the worst was Connie in III because she basically led the family into violence every time (if you'd even consider her the counselor of Part III, which i do). The best i would say is Vito for his brief time with Michael as Don-i mean after all he did warn him correctly of the assasination attempts.