How did Zoro lose his left eye? He never lost it. It is a scar over his left eye that has been there after the time skip, and many fans are theorizing on what might have happened to it. For example, Zoro has a hidden power sealed beneath his left eye, and when he opens it, a hidden power is unleashed.
He was asked to defeat the Humandrills on the island and, eventually, train with Mihawk as well. At some point, however, Zoro sustained an injury to his left eye. What exactly happened here remains unknown to date, however, Zoro's left eye has been closed ever since.
It's entirely possible Mihawk noticed through their duel and training that Zoro suffers from ocular dominance in his left eye. That is to say, the left eye is stronger than the right. As a result, maybe Mihawk scarred the left eye shut and instructed Zoro not to open it until his right eye was trained enough.
When his opens his eye, it will mean he gets this power-up ---------> There is no power-up. It just means that he is now in the full control and mastered Observation haki. His eye will still look the same. He will be able to do it unconsciously all the time.
In the manga, it showed he lost it by throwing the little blade of Mihawk, like he did for the cursed sword, but he wasn't ready for even the tiny little knife and he loses his eye.
Prior to One Piece's timeskip, Zoro's left eye was fully functioning and completely uninjured. Yet when the Straw Hats reunited after their respective adventures, Zoro's left eye was mysteriously scarred shut. Prior to the timeskip, his left eye had been seen glowing when using certain attacks.
In it, Zoro, while anxious to advance after showing progress in his training, is quickly humbled by his teacher, resulting in the loss of his eye.
It limits his sight and his depth perception in particular, and it would get hair in his open eye whenever the wind blows. You could say its because he's ashamed of his relation to Germa, but if he really cared that much, he would have just shaved the twirly bits off both his eyebrows, like he recommended Duval do.
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.
Zoro wanted to see if he was worthy of Mihawks little knife necklace thing so he threw it it the air (like his cursed sword) and it slashed his eye which meant he still wasn't worthy to wield that knife.
Regardless of how much stronger he was compared to the vast majority of the people he knew, deep down, he was aware of just far the gap was between him and his ultimate goal. This humbling affected Zoro on a deep level, so much so that it seems to have caused him to become much more serious.
Zoro and Sanji's differing philosophies
At the core of One Piece's most famous quarrel, the eternal bickering of Zoro and Sanji, are two foundationally different philosophies. The reason for this primarily ties into Zoro's backstory, particularly his upbringing in Shimotsuki Village.
After the two-year timeskip, Sanji now covers his right eye, shows his left eye, and has grown his hair just slightly longer.
Mihawk outclassed Zoro when the two fought over Baratie, and even now, he is superior to the straw hat swordsman in terms of skill. On the Sabaody archipelago, Rayleigh fought Kizaru and hit him in battle and even wounded him during the battle.
The reason is because Zoro understands exactly what Luffy means just by a look or by even Luffy calling his name. Luffy goes to Zoro the most out of anyone on the ship even for the smallest of things. He has proven to understand Luffy the first time when they met each other.
Enma is the strongest sword possessed by Zoro of the Straw Hat Pirates right now. What is Zoro's weakest sword? Sandai Kitetsu has to be the weakest sword Zoro has used until now in the One Piece manga and anime.
Over the years, he has come a long way and become one of the strongest pirates on the seas. Zoro has attained terrific strength, but he does not rely on a Devil Fruit at all.
Four members of the crew possess Devil Fruit abilities: Luffy, Chopper, Robin, and Brook. Luffy has awakened his fruit and has used its alteration of his body in a massive variety of creative ways to adopt new forms which increase his power and fighting capabilities.
Sanji was born in the North Blue into the Vinsmoke Family, the reigning royal family of the Germa Kingdom, along with his three brothers on the same day, with Sanji being the third son of the family, thereby making him the kingdom's third prince.
During his time on Momoiro Island, Sanji learns a move named “Sky Walk,” which allows him to jump to great heights and to be able to float mid air by making sonic booms in the air behind him.
Later on, in his fight with Queen, Sanji angrily realized that the genetic modifications that laid dormant within him since birth have finally awakened, granting him a superhuman physical constitution and an exoskeleton that makes him nearly invulnerable, including an accelerated healing rate.
He and Jimbei are currently the only known Seven Warlords who do not have Devil Fruit powers. The only duel between Shanks and Mihawk that was actually seen is in the game One Piece: Unlimited Cruise 2.
During this arc, Luffy and a hypnotized Zoro end up fighting, resulting in an X scar across Luffy's chest when he was wounded by Zoro.
SMH. Luffy got his scar on his chest from Roronoa Zoro this happened while Zoro's being controlled on Episode 223 from 10:55 - 11:10.