huh! I don't really feel much about any of them really, I was never one for princess movies as a kid & they are irrelevant to me now. But at gunpoint I would say Elsa....! She's angsty, her parents kept her isolated & locked up then DOIED, she has a complex from hurting her twee genki sister as a child... some part of her brain can, uhm, make Olaf, that's interesting. Her hair is fantastical color, she has powers...

They really hit a nail on the head with her, and then didn't learn anything at all from it and refuse to do what could make them a lot of money. Imagine any of their recent middling movies with that kind of protag instead... golly...! Frozen is an objectively Bad movie but aren't they all. Disney movies you kind of have to assess in terms of what kids could get out of them .... and sooo many, offer so little to really play with, chew on... they just refuse to fester.

Honorable mention answer is Kiara (: I used to essentially subconsciously copy Lion King 2's plot with my own plots as a child... she challenged all that prejudice Lion King 1 established as a hard rule...