I find it hard sometimes to root for Isobel. She means well and she often does good, but she's also a bossy know-it-all who is just as judgmental as those she judges and who fails to consider the ramifications of her plans on others. For the prime example, all of season two.
Anna and Mrs. Hughes are probably the two most "pure" characters in the series. Though I really began to worry about Anna this year with all the stuff surrounding Bates -- especially as I was ready for Bates to swing from the gallows just to spare us all from more tedious scenes of Anna fretting or Anna at the prison or Anna playing Veronica Mars.