A wiseman ever said to me that there were 3 things which could destroy the world. 

First, People who ONLY follow his personal desire.

Second, People who was Jobless and did nothing.

Third, People who had too much money and didn't know what to do (stingy)

Another wiseman said to me that there were only 2 things.

First, smart but wicked people.

Second, those who are expert in 'worshiping'  but didn't understand their own religion, A.k.a, intentionally stupid while using the religion for their own profit.

Meanwhile, 

most of all modern soldiers would said that the ONLY one which could destroy the world for sure was...

 [ WAR of NUCHLEAR ]