Roos can be very dangerous. Last drought in Canberra they were warning parents not to let kids loose around the shores of Lake Burley Griffin as they feared they could be drowned by a roo, as they were doing to dogs. We had a GSP once when we lived in the country, her mother and a brother were both killed by Roos as they liked to chase them.
If you think that roo has big guns, check out some of the big Reds.