Roronoa Zoro learned how to imbue his swords with Armament Haki during the two-year timeskip when he trained under Mihawk. Thanks to his guidance, Zoro has become incredibly good at this skill.
Sanji - Training With Ivankov
One Piece's Sanji was sent to the Kamabakka Kingdom, an island inhabited entirely by okama that happened to be the home of one of Luffy's newest allies, Emporio Ivankov.
Shichibukai Bartholomew Kuma sent Zoro to Kuraigana Island, where the World's Strongest Swordsman, Dracule Mihawk resided. The two years that Zoro had to his disposal were spent honing his skill under Mihawk's guidance. Like Sanji, he managed to learn the basics of Haki and improved his swordsmanship skills greatly.
Rayleigh took Luffy here to train him in the use of Haki for two years. He placed his Straw Hat on a rock during this time. Rayleigh spent the first year and a half to teach Luffy the basics of Haki. After Luffy mastered them enough, Rayleigh left him alone for the remaining half year to finish his training.
Heracles is a strange warrior that used to reside in the Greenstone forest in the Boin Archipelago. He trained Usopp in the use of Pop Greens for two years.
Rayleigh then said that he was going to teach Nami how to operate a coated ship. She was pleasantly surprised when she heard from Rayleigh that Luffy was already at the archipelago. After the ship arrived at Grove 42, Brook soon boarded the ship.
also unlike Luffy and Zoro, Sanji wasn't really trained by anyone, he wasn't being taught anything. He was learning and getting stronger by constantly fighting and defending himself. His training was basically like if Luffy was in Rusukaina without Rayleigh for the whole 2 years.
Zoro is the second-strongest member of the crew and that will most likely always be the case in the story. After defeating Kaido's strongest underling, King, Zoro was recognized as the strongest commander of the crew.
Well, Chopper is actually the youngest Straw Hat, and he is periodically treated as such. It is not unusual for Chopper to be babied by characters such as Robin and Zoro. His birthday is December 24th, Christmas Eve, which reflects the cold climate he comes from and the fact that he was originally a reindeer.
Roronoa Zoro learned how to imbue his swords with Armament Haki during the two-year timeskip when he trained under Mihawk. Thanks to his guidance, Zoro has become incredibly good at this skill.
He recognizes and respects the swordsman's code and he even permitted Roronoa Zoro the luxury of training at his hand for his dedication and selflessness. He is also unafraid to reference his title of "Greatest Swordsman in the World" in relation to himself, indicating a high level of confidence in his own abilities.
In his first appearance, Mihawk humiliated and almost killed the Straw Hats' Zoro, who also dreams of becoming the world's strongest swordsman. After that defeat, Zoro swore of defeating Mihawk, but he actually ended up training with him during the "two-year gap".
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.
After their eventual rescue, Sanji stays with Zeff for several years and helps him build a floating restaurant, the Baratie (バラティエ). Zeff in turn makes him a first-rate cook and teaches him his kick-based fighting style.
Silvers Rayleigh, also known as the Dark King, is a major character in the manga and anime series, One Piece. He is the former right-hand man of the legendary Pirate King, Gold Roger and later Monkey D. Luffy's Haki master and teacher, he is also Shakuyaku's husband.
Every Straw Hat Pirate is, without a doubt, loyal to their captain, and they will offer their lives for him in a heartbeat. Of course, fans can be certain that Luffy will definitely do the same. That said, there is one crew member who stands above the rest in terms of loyalty to Luffy: Roronoa Zoro.
3 Sanji. Because Sanji is limited to his feet in battle, the Straw Hat is ranked third on his list of crew mates. After picking up the chef as an addition to their group, Luffy and the others got to know Sanji as one of the strongest members of their ship.
As always, Nico Robin is one of the best-looking Straw Hats even in the Onigashima section of the Wano Country arc. For the Raid, Robin chose to wear a white kunoichi outfit with a daffodil pattern all over it.
As the Straw Hats' musician, it's little surprise that Brook is technically the least valuable member of the crew. He rarely contributes anything that would lead to the group's success and even needed to be saved by Zoro at Thriller Bark.
Luffy, who is undoubtedly the strongest Straw Hat capable of using Haki. One major argument for such a conclusion is his being able to use Conqueror's Haki, which he specializes in, as well as Observation and Armament Haki.
Nico Robin is the archaeologist of the Straw Hat Pirates and one of the crew's strongest fighters. While Robin should've been an Observation or Armament Haki user, given that she spent quite a lot of time around those who wield it during the timeskip, she doesn't equip this skill.
Zoro can eat 3 devil fruits.
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.