Conqueror's Haki is an incredible power in the One Piece world that only one in a million people possess. Like the other two forms of Haki, this power is not something that can be awakened. Instead, the user has to be born with it and, at some point in their life, they manage to gain mastery over this skill.
Conqueror's Haki is an extremely dangerous ability and it allows the user to impose their willpower on others. When this happens, the target usually passes out if the difference in power is significant. The advanced form of Conqueror's Haki is known as Conqueror's Haki Infusion. Only a handful of the strongest are known to be able to infuse their bodies or their weapons with Conqueror's Haki.
11 Zoro
Zoro is a swordmaster and an exceptionally powerful pirate. In the Wano Country arc, Zoro received the powerful sword named Enma and it helped him tap into his Conqueror's Haki for the very first time.
Using Enma, Zoro was able to coat his swords in Conqueror's Haki. He did this against King the Wildfire and ended up defeating him with his newly acquired abilities. However, Zoro cannot maintain this power for long and his usage of it is likely the weakest in the story so far.
10 Yamato
Yamato is Kaido's child and, thus, it is no surprise for the fans to know that she possesses the ability to wield Conqueror's Haki as well. Yamato was seen infusing her kanabo with Conqueror's Haki and using the techniques of her father, such as Thunder Bagua.
Her control over it is great enough to fight her father for an extended period of time with minimal damage.
9 Rayleigh
Rayleigh is a legendary figure in the One Piece world, famously known as the Dark King. It is no surprise to know that Rayleigh possesses the power to use all three Haki types and he has also acquired the skills of Conqueror's Haki coating, meaning he's among the handful of the strongest people in One Piece.
Rayleigh was seen using this ability when he confronted Blackbeard on Amazon Lily. He is very old right now, meaning this skill of his has weakened.
8 Garp
The Hero of the Navy, Garp is among the legends of the One Piece world and the strongest Navy officer to ever exist. Garp doesn't possess any Devil Fruit power and solely relies on his Haki in battle.
Garp is a user of Conqueror's Haki Infusion and fans saw him use this ability during his invasion of the Pirate Island. Garp's Haki is such that he was able to destroy a large part of the town on the Pirate Island with a single punch.
7 Oden
Kozuki Oden was the daimyo of Wano Country's Kuri region and the rightful Shogun of the country. Oden was an extremely powerful pirate and possessed great ambition. As such, him having Conqueror's Haki is not a surprise at all.
At some point in his life, Oden mastered the ability to use Conqueror's Coating. When he deployed this skill, he was able to scar Kaido. He could potentially have killed the dragon if wasn't distracted.
6 Luffy
Luffy is one of the Four Emperors of the Sea and a pirate worth 3 billion berries. He has advanced all three types of his Haki and his Conqueror's Haki reached the next level in the Wano arc.
Luffy learned the ability to infuse Conqueror's Haki during his fight against Kaido. Although his usage of this ability was rough at first, the more he fought, the more control he gained over it. Currently, Luffy is among its very best users.
5 Big Mom
Big Mom is a former Emperor of the Sea and, thus, it is no surprise to know that she is a user of Conqueror's Haki as well. In Wano, she demonstrated the usage of the advanced form of Conqueror's Haki when she took down Page 1, one of the Tobi Roppo, in a single punch.
Sadly, Big Mom did not make much use of this ability for unknown reasons when fighting Law and Kid. It is difficult to gauge how strong her usage of it is.
4 Kaido
The Strongest Creature in the World, Kaido is a pirate worth 4.6 billion berries and he ruled over Wano Country until recently. He fought against Luffy in Wano and demonstrated the ability to use Conqueror's Haki Infusion to the fullest.
Kaido's Haki was certainly superior to that of Luffy, however, he ended up losing the fight to him anyway. His Haki is extremely powerful and, given that he was known to be the strongest pirate, his proficiency in advanced Conqueror's Haki was very impressive.
3 Shanks
Shanks is one of the Four Emperors of the Sea in One Piece and likely the strongest of the current Yonko. He wields a legendary sword named Gryphon and, given that he has no Devil Fruit powers, Shanks solely relies on his Haki in battle. His biggest asset is his Conqueror's Haki.
Shanks can use Advanced Conqueror's Haki very well and he was able to dismantle the entirety of Kid Pirates with a single swing of his sword.
2 Whitebeard
One of the former Emperors of the Sea, Whitebeard was a legendary figure in the One Piece world. He was known to be the only pirate capable of rivaling Gol D. Roger in combat and this certainly made him special.
After the death of Roger, he was widely known as the King of the Seas, and rightly so. While he possessed a powerful Devil Fruit that gave him the power to destroy the world, Whitebeard also had an extremely powerful Conqueror's Haki. He was also a user of Conqueror's Haki Infusion and he displayed the skill when he fought against Roger on an island in the New World. This battle ended in a draw.
1 Roger
The Pirate King, Gol D. Roger is one of the strongest characters in the entire series, if not the strongest. Roger did not possess any Devil Fruit abilities. Instead, he relied on just his Haki in battle, making him an exceptionally powerful pirate.
Roger had control over advanced Conqueror's Haki and he displayed its usage in the fights against both Oden and Whitebeard. The fact that he was able to tie the fight with Whitebeard even though the latter possessed an extremely overpowered Devil Fruit on top of advanced Conqueror's Haki means that his Conqueror's Haki was likely much superior. Furthermore, Roger managed this while being extremely sick and this only goes to show that, in his prime, he was the greatest pirate.