@Fire Fist:
Viper was with them when they were climbing the mountain in Lal Mirch's flashback.
Personally I think it goes (from strongest to weakest)
Fon
Luche
Reborn
Verde
Colonello
Viper
SkullAnd yes, that's going by ROYGBIV. But it makes the most sense.
I really doubt Reborn or Colonello are that far down, Anyway they're all pretty strong aside from Skull, who just seems to be a joke. You must remember that their trials are all based on something different, so its impossible to draw up a strength list anyway.