The Four Emperors & The Eleven Supernovas

As an entity, the Yonko are one of the Three Great Powers of the world, the others being the Shichibukai and Marines.
Individually, the Yonko are considered to be the most powerful pirates in the world, as well as having a powerful crew. Because of their power, they can declare chosen locations as their own; the mere declaration is often enough for others, both Marines and pirates alike, to acknowledge their authority.

The 4 Emperors individually reside within the second half of the Grand Line (known as the “New World”), exerting impressive influence and control over dozens of other pirate crews and self-governing islands.

The Yonko themselves are not allied together as a coalition compared to the Shichibukai and follow their own individual paths. The possibility of two or more of the Yonko forming an alliance is enough of a threat to cause the World Government to panic, as seen when the World Government attempted unsuccessfully to prevent a meeting between Shanks and Whitebeard at one point in the series.

Because of their immense power, it is necessary for factions aiming to oppose them to first strike an alliance with other factions in order to bring the Yonko down. However, even with multiple alliances amongst powerful pirates, the chances of defeating a Yonko are still extremely low.

The Yonko Charlotte Linlin and Kaido both have a single Road Poneglyph that can, with all four Road Poneglyphs deciphered, lead to Raftel’s location.

All of the Eleven Supernovas are known to be involved with at least one Yonko:

• Monkey D. Luffy looks up to Shanks as a role model and personal hero, allied himself with the Whitebeard Pirates in the Battle of Marineford, wishes to dethrone Kaido and Big Mom, and despises Blackbeard for causing the conflict that led to his brother’s death.
• Roronoa Zoro, as a member of Luffy’s crew, is part of the alliance with the Heart Pirates to defeat Kaido, and most likely receives an amount of anger from the latter and Big Mom, due to Luffy’s behavior on Fishman Island and Dressrosa. He also considers Blackbeard an enemy.
• Trafalgar Law made an alliance with the Straw Hat Pirates specifically to take down Kaido, though as a pretext toward his real motive of eliminating Donquixote Doflamingo, hoping to anger Kaido into killing Doflamingo, and estimating a 30% chance of actually going on to beat Kaido themselves.
• Eustass Kid, Scratchmen Apoo, Killer, and Basil Hawkins all wish to dethrone Shanks, and were approached by Kaido after a failed suicide attempt. After unknown circumstances, Scratchmen Apoo becomes a subordinate of Kaido, and Kid, who seemingly fought Kaido, was badly defeated and told by Kaido to pass along a message to Luffy and Law that they should run for their lives after interfering with his plans.
• Jewelry Bonney was seen crying after Whitebeard’s death, and was later captured by Blackbeard, though managed to escape custody of the Marines after being captured by Akainu.
• Capone Bege is currently a subordinate of Big Mom.
• X Drake is currently a subordinate of Kaido.
• Urouge was shown talking to Kaido about his motives for suicide, but beyond that he seems to have the least interaction with them.