If USA/Russia/China are the 3 most powerful countries, who are 4,5,6,7,8,9,10 ?

[Dereich]

Since 2014 Brazil's economy has taken a nosedive and its political situation has turned unstable. I doubt people today would be inclined to put them in the top 10. In Brazil's place I'd put either Turkey, South Korea, and Saudi Arabia. Saudi Arabia is probably the best answer; its soft power has been enormous in the Muslim world for decades and its military is one of the best funded (and with its recent interventions probably among the most experienced top) in the world.

China should absolutely be at second. Economic wealth (and the soft power you get from that) really makes the difference. China is able to invest and spread its influence through Africa and South America. Russia has trouble exerting power with its neighbors. The hacking and election influencing boosts Russia, but we don't really see it all that much outside of Europe and its success has been limited. Unless I see them actually succeed at building a new international coalition, China gets second.

So my list would be:

1.United States
2.China
3.Russia
4.France
5.Britain
6.Germany
7.Japan
8.India
9.Saudi Arabia
10.Italy

[Dereich]

In Brazil's place I'd put either Turkey, South Korea, and Saudi Arabia. Saudi Arabia is probably the best answer; its soft power has been enormous in the Muslim world for decades and its military is one of the best funded (and with its recent interventions probably among the most experienced top) in the world.

the country that even with billions of dollars spent on US toys can't beat a few thousand Yemeni tribesmen with dusty AKs? 

You can use that same logic against the US in Afghanistan