If people say that all human individuals and groups have the propensity of violence in them, I don't disagree with that but I would add that certain groups seem to have a more aggressive warlike nature than others.
Some people I can think of just the top of my head with a very aggressive national character:
1. Mongolians
2. Turks
3. Burmese
4. Jews
5. Germans
6. Somalians
The reason why who knows. Likely a mixture of genes and environment.
Obviously, all ethnicities have propensity for aggression but these groups groups stand out the most imo. You'll regularly encounter aggression or are much likely to encounter aggression from these peoples. For most other people of the world, its a friendlier national character with some typical minor passive aggressiveness. Russians are odd in that they can be exceptionally friendly yet quite very similar to the groups I just mentioned. Vietnamese, Cambodian, and Lao people can display a lot of aggression as well but theirs is more due to an extreme inferiority complex. Anglos are quite like the groups I just mentioned above but display some civility as well as the need to show some finesse in masking their aggressive national character.
Like how some breeds of chicken or dogs are more aggressive than other breeds, same with humans. Some specific groups of nationalities simply need to be checked more than others.
Least aggressive peoples with friendly national characters would be the scandinavians as well as most of east asia and south east asia. Thats not to say that these groups like other people in their nations, just that theyre consistently much less aggressive than other peoples.