a wicked fiend的用法和样例：
- The little boy had a wicked twinkle in his eyes.
- He plays a wicked game of bridge.
- She is in the grasp of a wicked man.
- A wicked curve ball; a wicked imitation.
- A wicked prank; a critic's wicked wit.
- She got them to hand over all their money by a wicked deceit.