Use "deadly enemy" in a sentence

1. Never again would the human race face a deadly enemy

2. 8% sodium chloride, the favorite of fishes but a deadly enemy of man

3. evil; but the weather may prove a more deadly enemy than any

4. In the Middle East, the United States was helping the Israelis and Palestinians to feel their way towards peace, little realising that it would soon face its most deadly enemy – al-Qaeda