Answer:
North Korea
Step-by-step explanation:
North Korea is the country that has threatened world security in recent years because of its interest in becoming a nuclear power. Its leader wants to impose himself as a world figure and uses the threat of nuclear weapon as a bargaining chip.
Venezuela : The country is on the verge of a civil war, totally collapsed, not a threat to the world, but to its people yes.
Vietnam: No major conflict happening there now, and certainly not an emerging nuclear power.
Iraq: still recovering from wars... not a nuclear threat.