I have been thinking a while what could be the criteria of getting Conqueror’s Haki (Haoshoku Haki).
Literal Meaning of Haoshoku
The literal meaning of Hao is supreme rulers. A twitter user called it “overlord”. So the word literally means lord of the lords, king of the kings.
As Marigold says in chapter 519:
Viz missed half of her quote which is: “He has the quality of a king, meant to stand on the shoulders of other men!!”
Based on Haoshoku’s literal meaning and Marigold’s statement, a Conqueror’s Haki wielder has to be => 1) a natural born leader.
There is another interesting meaning of Haoshoku which I found from wiki => “Though the “Haō” is translatable to king, it refers to a warring king or conqueror, one who rules by power and conquest”.
Based on this translation the second requirement can be => 2) a king of warriors – extraordinary fighter.
The most important information about Haoshoku Haki came from the Dark King in chapter 597. The first thing Rayleigh says about Haoshoku, “it is the power to overwhelm — the color of the supreme king”
It is the ability to overpower the opponent’s will.
An exceptionally strong willpower to the point it can overwhelm opponent’s will is the core of Conqueror’s Haki. That’s why Conqueror’s Haki intimidates weaker opponents and break their wills to fight back. We have seen several times how fierce animals ran away because of Conqueror’s Haki. So the third quality of a king => 3) exceptional willpower.
Rayleigh also said, “It can often be found in the type of people who make a name for themselves on a global scale“
So the next criteria can be => 4) fame on a global scale.
Chijao asked Luffy, “What king do you seek to be?“
This statement implies the Conqueror’s Haki users are typically aiming for a title/throne. That’s why the next criteria can be => 5) ambition to be a king.