Good to see you again Hookbill,
I do have an example, but not exactly one of the greatest or most puissant characters of Middle Earth!!
Lobelia Sackville-Baggins
Now as we all know she starts off mean and spiteful and money-grabbing, determined to wrest Bag-End from the Bagginses and add to her silver spoon collection. After Sharkey's ruffians took over the Shire she 'went for' one of them with her umbrella on being insulted and off to the lockholes they dragged her.
On her release she was cheered by the crowd, became popular, but was crushed by the loss of her son, she returned Bag End to Frodo and retired to Harbottle. Dying the next year, she left all her money to help hobbits made homeless by the troubles.
I'd say that was a pretty good turn-around