It depends upon how you record an act of violence, but Colombia and South Africa top some of the more obvious lists:
Violence measured by mürder rate per capita:
http://funadvice.com/r/bhkkoqknrb2 ..... puts Colombia at #1 and South Africa at #2.
Violence measured by homicide using Firearms per capita:
http://funadvice.com/r/14urllrlkls ..... uts South Africa ahead of Colombia.
Assaults per capita puts South Africa top of the league tables:
The site also has various other tables that could be used to quantify levels of violence in various countries.
Best wishes - Majikthise.
Britain in 2009, was named the most violent country in Europe. The Unites States though, is sadly the most violent of them all. We may thing it is the middle east, but the U.S. out-beats them. Our violence, rap(e), killing, etc. is very high, compare to other countries.
I hope this helps. Its a sad conclusion, If I must say, but it is true.
The USA ranks high not only in the "retail" violence that you refer to, but also in our institutional violence at home (death sentences, rate of imprisonment, etc.), our military violence abroad, and our technological destruction world-wide of the biosphere and its supportive planetary systems.
It depends what kind of violence you're talking about. Some countries are more violent than usual because of wars or civil unrest and then others are violent because of crime.