Roger. Conqueror's Haki, also known as the Haki of the Supreme King, is the rarest form of Haki that only a few people in the world of One Piece are born with. Unlike the other two Haki types, Conqueror's Haki can't be learned through training and is only possessed by those who are born with the spirit of a king.
Roger used advanced forms of conqueror's haki as he imbued his sword with conqueror's haki and clashed with Whitebeard. He also used advanced armament haki for more powerful sword attacks. Additionally, Roger possessed the observation haki, thus, making him the strongest haki user of all time in One Piece.
Zoro was the first person who accepted Luffy's invitation and joined the latter on his journey to become the Pirate King. Zoro is a very powerful fighter and he possesses all three types of Haki. Zoro was able to use Conqueror's Haki unknowingly against Kaido.
Monkey D. Luffy has mastered all three types of haki, including Kenbunshoku Haki (Observation Haki), Busoshoku Haki (Armament Haki), and Haoshoku Haki (Conqueror's Haki). He can even use several subforms of the hakis, which makes him one of the most powerful haki users in the One Piece world.
In the anime, the user of Haoshoku Haki has a dark purple aura around him.
Conqueror's Haki is one of the rarest powers to exist in the One Piece world. Unlike the other two Haki forms, this power isn't accessible by everyone but exists within only a chosen few. Its basic level allows the user to intimidate and overwhelm those who have weaker wills.
Appearance. Zoro is a tall, muscular young man with lightly tanned skin and black eyes. He always carries his three swords along with him, bundled up with a green haramaki over his right hip, allowing him to easily draw them with his left hand.
5 Armament Haki Subtype 4: Internal Destruction
The rarest subtype of Armament Haki, known as Internal Destruction, has only been demonstrated by two characters — Monkey D. Luffy and his mentor, Silvers Rayleigh.
Kenbunshoku Haki, one of the three Haki types in One Piece, grants the most powerful pirates unfathomable abilities. From sensing people's morality and emotions to being able to predict movements in battle, this form of Haki allows users to tap into a sixth sense that provides impressive precognitive abilities.
As fans know, Nami doesn't wield any form of Haki in the story so far. Haki is a power that Rayleigh described to be the manifestation of the user's spirit. Every person in the One Piece world possesses Haki, however, not everyone is able to bring this latent skill out.
Busoshoku is perhaps Luffy's most used Haki as he commonly mixes it with his Devil Fruit abilities to increase his offensive and defensive potential.
The circumstances surrounding Zoro's left eye aren't a complete mystery; at the very least fans know that it happened sometime during the two-year time skip. During this time, each member of the Straw Hat crew committed to training and growing stronger.
Garp has always been portrayed as possessing incredible physical strength and as a master of the more common form of Haki, Busoshoku (Reinforcement). However, the reveal that he has Conqueror's Haki comes as a surprise, as this power usually belongs to individuals with extreme ambitions, known as Supreme Rulers.
Sanji is also a skilled user of Armament Haki and he has displayed the skill on several occasions, especially in the Wano Country arc. To defeat Queen the Plague, Sanji used his Haki to coat his body and improve its durability against the high-temperature flames of Ifrit Jambe.
Sanji can use conquerors haki but the possibilities are very low, so it's either he gets a new move develops his armament/observation haki, or gets a new form of haki that will deem him worthy to be one of the major fighters in the straw hats crew.
Despite its great capabilities, the Haki in a person's body is not limitless and it can be depleted from overuse, rendering the user unable to use it for a set period of time while it regenerates.
Whether Shanks can defeat Kaido or not is unknown, but he is certainly on par with Kaido, if not stronger. Interestingly, the two have already fought once in the New World, and Shanks emerged unscathed at Marineford after the fight.
The Haki Haki no Mi (覇気覇気) is a Paramecia-type Devil Fruit in which the user is able to see all three types of Haki, as symbolized by a different color.
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".
As a testament to his power, Ace is one of the rare few characters to possess all three. In the main story, however, he is only seen using the Conqueror's Haki, making use of the other two in supplemental materials.
This is to relate to his Devil Fruit ability, the Mera Mera no Mi, or the Flare Flare Fruit. As such, the orange color of Ace's burning flames is also a big indication that his color is, in fact, orange. Furthermore, even his Devil Fruit is orange in color. RELATED: One Piece: What Are The Advanced Haki Forms?
The Armament haki (busoshoku) is the ability to project your spirit into armor. An example of how it represents one's spirit is Vergo's purple haki as per debut. Vergo maybe mastered his armament haki. So this purple tint to his haki could've been his spirit's nature, the same to Luffy where he got his own shade.
Garp and Tsuru are the only two vice admirals to have special shoulder-pads; Garp is golden and blue (black and red in the anime) while Tsuru is purple with white dot whereas the standard color is blue and red.