The country I fear most is Pakistan. If the fundamentalists take over...oh god.

The US, EU, China and Russia are very dangerous in my opinion. China wouldn't be ready for war but they are rising so fast...

The country I fear not at all is India.

North Korea I think just plays a game...they feel threatened and want to show that they have weapons, even if they haven't any.

Iran is threatened itself like North Korea and I suppose that's the reason why they probably want the nuclear program. But a war against Iran is more present than a war started by Iran so I fear not really Iran, but those who plan to attack Iran.

Countries aren't the biggest threat to world peace.
It is particularly the arm industry, the military, separatists and fundamentalists who become terrorists (indifferent if they are extreme left-wingers or extreme right-wingers or Islamists). The point is that terrorism, war, crimes and civil war couldn't exist without the arm industry. Fun fact?

Basic materials and the climate change are and will be the causes of war also.