It is necessary to determine what "format" of the country we are considering. If we take totalitarian and "medieval regimes" - then there all greatness is reduced to a huge, preferably poorly educated population, a huge army with almost unlimited human resources and aggressive policy, both in relation to its own population and neighboring countries.
If we talk about more civilized and developed countries, it is worth considering a set of indicators:
External:
Weight in world politics, economy, army, technology, ...
Internal:
Education, standard of living of the population, economic and universal freedoms, quality legislation, accessibility of education and medicine.