A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion reactions.

The country with the highest number of nuclear warheads, is being considered world power.

See below

Russia – 6,257
Usa – 5,550
China – 350
France – 290
UK – 225
Pakistan – 165
India – 160
Israel – 90
North Korea – 45

In other words, Russia is the most powerful country in the world right now, followed by USA. Though the United States always claim to he the strongest, it seems not to be so from the look of things. As a matter of fact, USA import crude oil from Russia.