Definitely the Evil Queen, though not based off any Snow White movie, but rather the Once Upon a Time series.
She's very unpredictable but certainly not heartless, at least in Storybrooke that is. Plus she's really reformed herself in the past season, though she still can be a little evil from time to time.
I certainly don't like Jafar in Once Upon a Time in Wonderland, however, as he's just a psycho who wants all the power in the world.
The only other villain up there that plays a significant role in Once upon a Time is Captain Hook, and I have mixed feelings towards him, to the point that I wouldn't care much if he was the major character that is rumored to die later on this season.
I'd be FURIOUS if it was Regina (a.k.a. the Evil Queen), however.