Unlimited - If your opponent only has 1 Pokemon in play
you could potentially win on turn 1 by Wallying or Rare
Candying then using Ghost Head. Otherwise Banette is bad
Modified - Banette has a lot of hype, but I don't know
if I buy into it yet. After Ascending to Banette turn 1
from Shuppet CG, you can follow that up with either a
turn 2 Ghost Head or Spiteful Pain. Use Banette with
Trainers like TV Reporter to increase the odds of
getting a Banette in your discard pile.
The resistance to Blissey is nice, but Blissey may be
able to overcome it just by stacking tons of energy.
Weakness to Honchkrow sucks.
Overall I just think this Pokemon's attacks don't have
enough oomph, and it doesn't have enough HP. 2/5
Limited - It's unlikely you'll ever have a Banette in
your discard pile, so Spiteful Pain is limited to 40
damage pretty much. You could get a surprise KO with
Ghost Head. 3/5