You can't put any particular country on that list, most of the largest killings in world history took place there after the gun bans. Here is a good link if you want to see the actual records. While it is true, we rank high on the list of numbers, but so do MANY other countries, even with strict gun control. And one of the worst ever took place in 1927! So its not exactly a new problem.
List of rampage killers - Wikipedia, the free encyclopedia
Also, not ALL were done with guns.