If you count the power of a passport as Henley Passport Index 2006 to 2018 the number of countries you can travel to without a visa, Sweden, Finland, France, Italy, Spain and South Korea have the third most powerful passports in the world. They all can access 187 countries visa-free. Japan takes the top spot with 189 countries. Germany and Singapore is second with 188 countries.
At the bottom of the list you find Afghanistan and Iraq, both of which can visit 30 countries without visa.
The statistics comes from Henley & Partners Passport Index.