Darcy’s blog has this interesting post:
Charlotte was Blood-Thirsty: Character Paradoxes
Charlotte, from E.B. White’s Charlotte’s Web, is remembered as a character of great warmth for her friendship with the unlikely pig, Wilbur. Poor Wilbur, once the runt of the litter and saved only by the whim of a girl, is fattened up and ready for slaughter. (This is a story set on a working farm and, as such, it’s not a story of cruelty, but of practicality.) Only the spelling abilities of Charlotte save him.
Read the rest and see how you can work paradoxes into your characters.