3 Great Powers

The Three Great Powers
Not much is known about them except for the fact that they seem to be a very vital part of the World Government. There seems to be some sort of balance between the Three Powers. The Gorousei fear that if this balance gets disrupted, the whole world itself could fall apart. This has not yet been explained so far as to why one of the Three Powers being weakened could pose such a dangerous threat. One possible reason may be that the World Government or the Gorosei themselves play these various Powers against one another to insure that no single insitution becomes too powerful.

The only other thing known about the Three Powers is that they are collectively the reason why the Grand Line is called the Pirates' Grave.

The Three Powers have not been explicitly named as of yet. The only one that has been labeled as such are the Shichibukai. However, considering the animosity that seems to exist between the Shichibukai and high-ranking Marines, the latter organization is a distinct possibility for one of the other two Great Powers, especially when its considerable size and power are considered.

3 Admirals

Shichibukai

The 4 Pirate Emperors