-First, Luffy cut below his eye in chapter 1, giving him his iconic scar. -A lot of symbolism with losing left eyes. Zoro lost his left eye, Whitebeard lost a chunk of his head on the side of his left eye, Luffy himself is even left handed.
Unfortunately, Shanks turned him down repeatedly because he was too young. In order to prove his courage to the pirates, Luffy took a knife and stabbed himself below the left eye. The act resulted in a scar that certainly made him look tough as a pirate.
First, as mentioned in the previous section, Luffy has tried to stab his left eye before and Oda has drawn him with an eye patch on his left eye.
Since Luffy's Devil Fruit is actually a Mythical Zoan instead of a Paramecia, it granted him a completely new transformation instead and typical of Luffy, he ended up naming it Gear 5. In this form, Luffy gains a completely white transformation and takes on an appearance similar to that of the "Sun God" Nika.
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.
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.
Usopp remains to be the weakest member of the Straw Hat Pirates. In Wano, the vast majority of the members of the Straw Hat crew received good power-ups. However, Usopp was one of the members who did not receive any power-up and thus is lagging behind.
Luffy's greatest power-up to date is, undoubtedly, Conqueror's Haki coating. During his fight against Kaido, Luffy observed Kaido coating his weapon in Conqueror's Haki. After this realization hit him, he was able to use a crude version of this technique himself and could coat his fists in Conqueror's Haki.
The more he laughed, the better he seemed to fight. Throughout the clash against Kaido, fans could see him laughing even though he was fighting a high-intensity battle, which just goes to show how important it is to his character.
Luffy has lost teeth before in a comedic fashion (Skypeia) and Usopp has lost teeth in battle (Alabasta, etc) and they have always come back.
Luffy has allowed other people to wear his hat. The most well-known example is Nami, but Usopp and Tama have also worn his hat as well. In addition, Nico Robin and Sweet Pea have also worn Luffy's straw hat without his permission.
It has been damaged twice in the manga canon. The first time it was damaged by Buggy when he was fighting Luffy. Buggy spat on the hat as well when he learned that it previously belonged to Shanks. After the fight, Nami repaired it for him.
Luffy, however, has maintained that he is always serious during fights. In most cases, once he starts to fight he maintains a serious attitude and is only seen laughing once he defeats the enemy or is certain the enemy will be defeated, like in Buggy's case when he laughed before sending Buggy flying in the air.
He does not smile for quite some time following his victory, because he continues to go through troubling situations. Four episodes pass until he finally smiles again, once he makes a "safe" landing on a building with Nami after using his Devil Fruit powers to trapeze through the air.
In fact, I'm going to tell you exactly which episode of One Piece features Luffy getting his scar so you can NOT watch it. It happens in Marineford in episode 487 right after … Ace dies.
While the effects of this technique have been mitigated in post-time-skip One Piece thanks to training, the prior uses have already caused irreversible damage to his body. Luffy dies from gear 5th strain on his heart and law gives up his life so they can win. This causes Luffy to go into gears without dying.
As of now, the answer is no. Luffy has unlocked 5 Gear techniques, with Gear 5 being his peak form. There exists no Gear 6 technique at the moment. But we hope that Luffy will be able to level up the Gear 5 technique to surprise us with a new Gear 6 form in the final saga of One Piece.
Gear 5 is Luffy's pinnacle power, and he can do anything he wants in this form. Furthermore, it is mentioned that his powers are only limited by his imagination. With this gear unlocked, Luffy is said to resemble the “Warrior of Liberation” — Sun God Nika, who is said to bring smiles, joy, and freedom to the people.
Against Shanks, even if Luffy possesses weaker Haki, the Devil Fruit abilities of the Hito Hito no Mi, Model: Nika can make up for the deficit and see him emerge victorious. Currently, however, Shanks is likely stronger than Luffy, simply due to the fact that the plot demands that of him.
Luffy. There is no doubt that Luffy is the strongest and most powerful Straw Hat Pirate in existence. Luffy has always been considered one of the best fighters in all of One Piece, something that he proved more than once during the Land of Wano arc.
Immediately after the Water 7 saga came to a conclusion, we were introduced to Brook– the Straw Hat with the most tragic past! It's frankly commendable how Brook managed to endure 50 years of sorrow and loneliness. Big props to him for managing to live through such experience without losing it.