A profligate fails to return的用法和样例：
- You will be fined if you fail to return them to the library in due time.
- It's a sight that never fails to thrill me.
- A good teacher never fails to try his best to answer his students.
- That is to say,we must never attack others without provocation,but once attacked we must never fail to return the blow.
- It fail to stimulate a surge of investment in industry.