Board Thread:Show-Related Questions and Answers/@comment-28745829-20160614081826/@comment-25926288-20160614131330

I pay intensely close attention to Once's magic and its corresponging magic system. What you noticed is simply one of the many broken portions of Once's magic system.

Once pretty much did CDA's "Fairytale magic" sort of thing in the beginning, but as fairytale magic goes...."Arbitrary Deus ex Machina".

For transformatiom/ transfiguration spells, I personally headcanoned that more powerful magic users can change weaker ones, but not the other way around, without at least weaking them. For example, Rumple was able to glamour Regina, leading her to not being able to use her magic and undo it, while we never seen her even try anything close to that to Rumple.

So, for turning people into a "pile of ash", it's more a disintegration spell. Rumple makes some sense as he's top tier in magic, but Zelena and Regina can do so as well. I assume based on what is shown that you have to learn the spell (which they never give us details on how each spell actually works) than it's an option.

So, no resistance, unless you are immortal or somehow protected from another's magic. At any given rate, Zelena in season 3 should have just turned Regina into a pile of ash and swept her remains into the sewers, but then the show would be over XD

Note: It is a flick of the wrist. Jafar (+ Amara) even disintegrated a room full of people like nothing.