a mortal enemy的用法和样例：
- "A man who holds a sword in his hand, and sees a mortal enemy within reach of that sword, and does not fight, is a coward!
- Clearly, you don't want to make a mortal enemy of someone who will be in power for a while.
- A mortal enemy;a mortal attack.
- He would pull endless wires in order to meet some man who admired his work and was able and anxious to be of use to him-- and would proceed to make a mortal enemy of him with some idiotic and wholly uncalled-for exhibition of arrogance and bad manners.
- There was not a mortal man in the park.