great power vs country

great power and country both are nouns.

Word	Noun	Adjective	Verb	Adverb
great power	Yes	No	No	No
country	Yes	No	No	No

As nouns, country is a hypernym of great power; that is, country is a word with a broader meaning than great power:

great power: a state powerful enough to influence events throughout the world
country: a politically organized body of people under a single government

Other hypernyms of great power include body politic, commonwealth, land, nation, res publica, state.

great power (noun)	country (noun)
a state powerful enough to influence events throughout the world	a politically organized body of people under a single government
	the people who live in a nation or country
	the territory occupied by a nation
	an area outside of cities and towns
	a particular geographical region of indefinite boundary (usually serving some special purpose or distinguished by its people or culture or geography)