Best villain EVER!

I mean, I love seeing Regina, but it felt kinda... unnecessary? Regina's already reformed; there isn't really a point to still see her in flashbacks as the Evil Queen, and her scenes in 5x13 in flashbacks didn't really add to her character development.

^ True, but it did add to Snow White's development as a character in the episode. It was because of her wanting to destroy the people's faith in Snow White that caused the conflict, which would ultimately lead to Snow White finding her inner strength. Plus in the present, it did show the irony of how Regina, who was originally trying to destroy Snow White, was now the one having Snow embrace who she was and no longer being Mary Margaret.