well it mentally I think Cinderella because after her father died she was bullied, but still believed in hope and had faith things would get better. I think that makes mentally powerful. Physically I think Elsa is most powerful because she has magic and can make people fear her and love her. But honestly I think all the royals have their own power within and that makes them all powerful.
Physically speaking....... Elsa. Her powers could cause destruction.
However, Rapunzel's power is Resurrection. You could be dying and she could decide whether or not to save you. Ariel can communicate with Animals though! and Pocahontas can paint with all the colors of the wind! ;p
