After all, he is of the D. family and is considered one of the more dangerous member of the Worst Generation, yet he cannot use Conqueror's Haki.
6/10 Will Unlock: Trafalgar Law
A man of Law's stature is bound to unlock conqueror's haki at some point in the future of the story. Furthermore, Law is also a rival to Luffy and Kid, both of whom are stated to have conqueror's haki, so it only makes sense if he does as well.
Also known as the Snake Princess, Boa Hancock is the leader of the Kuja Tribe and one of the strongest characters in the series. As a Queen, it is no surprise to see that she has the power to use Conqueror's Haki — an ability that is only possible for those with a regal spirit.
Though it is confirmed that Law indeed does posses armament haki in his vivre card.
Currently, Kid is fighting Big Mom alongside Trafalgar Law. Kid was confirmed as a user of Conqueror's Haki by Kaido. Whether or not he has control over his Conqueror's Haki is unknown.
One Piece's weakest Conqueror's Haki user is undoubtedly Eustass Kid. He's shown no signs of training or skill with the technique, as well as showing no signs of Advanced Conqueror's Haki. While it's likely he eventually becomes more skillful with it, Kid currently ranks as the weakest user of the form in the series.
Nami is also a competent fighter, although among the weakest in the crew. She mainly makes use of her wits in combat to get the better of her enemies. Surprisingly, One Piece 1058 showcased her using Conqueror's Haki in what appeared to be a gag scene.
Law possesses the ability to use Kenbunshoku Haki. During the Raid on Onigashima, Law demonstrated great skill in this type of Haki as he was able to sense that Luffy was defeat by Kaidou, and was also able to sense Luffy Devil Fruit Awakening.
It's no surprise that Luffy possesses the power to use all three types of Haki, being someone who aims to become the Pirate King. In fact, Luffy has successfully taken his Armament and Observation Haki to extreme levels, making him a magnificent pirate in the process.
Advanced Conqueror's Haki users are very rare in the One Piece world, but Dragon is certainly going to be one of them, without a doubt. According to Kaido, only the very strongest in the world can make use of it, which Dragon certainly is.
So far, Sanji has not shown the ability to use the Color of the Supreme King, also called Conqueror's Haki, however, he could very well have this power.
Law-a former Shichibukai and does carry the "Will of D".
Law is known to use Haki only the basic one Law dont rely too much on them since he rely on his DF.
4/12 Armament Haki Subtype 4: Advanced Ryuuou
So far, only two characters have shown the ability to use it, Rayleigh being one, and Monkey D. Luffy being the other. Although Rayleigh seemed like an expert at using it, Luffy has only managed to use it subconsciously.
Despite its great capabilities, Haki is not limitless as it can be depleted from overuse, rendering the user unable to use it for a set period while it regenerates.
While Haki can bypass the devil fruit's defence, it doesn't negate the devil fruit, like Sea-Prism Stone does. Instead it "forces the devil fruit user's body into solidarity".
Yes he can. He can use all 3 types of haki, being armament, observation and conqueror haki.
8/10 Sabo Can: Haki Control
It is not a hidden fact that Sabo is extremely good at using Haki. Sabo was dangerous even without having a devil fruit.
He does now. That is perfection in a sense that he mastered how to control it.
Yamato is the son of Kaido so there is absolutely no surprise that he possesses the power to use Conqueror's Haki as well. Yamato awakened this power at the age of 8 and has, since then, been training it. By the age of 28, Yamato is one of the strongest Conqueror's Haki users.
Usopp's unique application of Conqueror's Haki
Usopp could also use this Conqueror's Haki to try and manipulate his opponent's perception of his own presence. Essentially, Usopp could become the ultimate sniper by making himself invisible to his enemies, essentially imposing his will onto them.