I dunno about each, but when Cinderella pulls out the other slipper, it's a spectacular Oh Snap moment and it's awesome to see.

Also, Pocahontas jumping in front of John. It was dangerous obviously but incredibly brave. Same for Anna saving Elsa.

Merida: "I'll be shooting for my own hand!" I love when she removes the hood, declares herself as first born and eligible for the contest and shoots down the 3 precise arrows. She was fierce!
Belle: "You should learn to control your temper" - very logically she gives her own piece of mind to Beast and finishes off with a kind thank you note to clear off any lingering bad feelings.
Ariel: the whole song of part of your world is just amazing. It encapsulated Ariel's character, her determination, her dreams, her zest for life.
Mulan: when she refuses the emperor for the greatest honor and goes back to home