Does the world need a policeman?

Does the world need a policeman?

Yes. In the history of the world it is clear that evil strong men/powers will use their strength to impose their will on others in unfair and unjust ways. 

Is the UN and effective police force. No.  In the history of the UN it has proven, except in a limited number of cases to be incapable of protecting others from evil strong men/powers. A key reason for this is that two countries, one of which is strong, at least military, and evil, being Russia, and the other being strong (at least getting there) and, if not evil, having values quite different from freedom, being China, have veto power over the UN Security Council. 

If the world needs a police force and if UN cannot be counted on to be an effective lead force what should we do?

Where and if possible, broad coalitions of freedom based countries should form coalitions to help protect people in countries that are being threatened or attacked by strong evil men or powers. This could include NATO in some circumstances but if/when necessary might consist of whatever coalitions that can be formed. 

And, at times, it may come done to the leadership, bravery, ability and capabilities of one country. 

If you had to pick one country that had the combination of military, economic, and moral authority, which country would you pick?  I know that I would pick the US even with its imperfections.