A superpower is a country that holds a great influence in the international arena due to a great political, economic, scientific, and military power. An important requirement in order to be a military superpower is the possession of nuclear weapons, because of the deterrence power that these weapons bring in international conflicts. In this sense, Russia, China, and India fulfill those requirements, the three of them have nuclear weapons and are big military powers, and the three of them excerpt a great influence in the international arena thanks to their advance and powerful political and economic resources.
On the other hand, while Brazil is a regional power in South-America because it has the largest economy and the strongest military in the region, it lacks the possession of nuclear weapons. Also, Brazil is subject to the political and economic instability that weakens its power of influence in the wider international arena. For all these reasons, Brazil cannot be considered a contender for superpower status today.