The actual number of dead will never be known as many countries did not keep accurate records at that time and the massive numbers of dead and wounded was too much for any country then to track. The following numbers are the currently accepted and verifiable by records and estimates.
The greatest single lose of life occurred in Russia - 3,311,000 military & civilian.
The greatest percentage of dead occurred in Serbia - 725,000 military & civilian out of a population of 4.5 million or 16% of the total population died during 1914-1918.
Total dead for all sides in the war = 16,543,185 (again military & civ.)
The Allies lost 9,386,453.
The Central powers lost 7,153,241.
Poland had the highest population of Jews in the whole of Europe at that time, and consequently lost the most.
France
spain
germeny
Egypt is the most populous Arab country period. It also has the highest population of individuals who identify as Arab.
Russia
Serbia
Poland had the highest population of Jews in the whole of Europe at that time, and consequently lost the most.
their country was demolished and they lost most everything
The Soviet Union :)
France
ww1 begins
China is the largest country in the world by population.
spain
The USSR, suffered numerous millions of deaths, mainly on the eastern front.
The population of Indonesia is over 200,000,000 and most are Muslim. The next country is Pakistan -Population nearly 200,000,000
India