Shanks brings the legendary Devil Fruit to East Blue, where Luffy ends up eating it by mistake. Therefore, Shanks gives up his arm to save Luffy, a child of prophecy who will bring a great change in the world. This sacrifice acts as a catalyst for Luffy to become King of the Pirates and to fulfil his destiny.
By this point, Luffy has eaten his Devil Fruit, which means he can't swim. He nearly dies, and Shanks, in rescuing him, loses an arm to boot.
In some ways, they are able to negate the loss of limb one way or another, and most of the time were as strong or may even be stronger than before. Here is how it goes. Sometime later in the series, Luffy had to sacrifice his arm (left or right) in a fight.
The previous battle between Kid Pirates and Red Hair Pirates
While the circumstances weren't fully explored, at one point, during his imprisonment in Wano, Kid revealed that they were defeated and that he lost his left arm in the process.
Apparently, Shanks didn't get any weaker from losing his arm
The Paramount War came to an abrupt end when Shanks made his appearance, which is another testament to his abilities. He certainly hasn't gotten any weaker since losing his arm.
Whilst in Foosha Village, Shanks found Luffy to be an incredible and endearing kid, so much so that he gave him his precious straw hat as a sign of his faith that he will become a great pirate.
Luffy has not surpassed Shanks just yet, otherwise, their future fight would hold no significant value. Luffy is close to Shanks in terms of power and it is only after their fight that he will officially be able to call himself stronger than Shanks. For now, Red Hair reigns supreme.
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.
However, that all changed after Chapter 1079, which saw Shanks defeat Kid and his crew in a decisive fashion and claim one of the final resources needed to claim the title of Pirate King.
Luffy falls off Onigashima defeated.
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.
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.
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.
While One Piece has many superb side characters, Big News Morgans just proved why he is the best of them by betraying Luffy and his crew. This may not seem like an action that would endear Morgans to One Piece's fans, but his reasons for doing this give him a delightful layer of complexity.
Throughout his journey Luffy has made strong bonds with numerous women. At least two have fallen in love with him, Alvida and Hancock, whilst another two have become enamoured with him, Rebecca and Shirahoshi. Nami, Robin and Vivi all share close and deep bonds with Luffy and have become some of his closest friends.
5 Pudding Betrays The Straw Hat Pirates
In the Whole Cake Island arc, Pudding tried to help the Straw Hat Pirates, however, she was actually leading them into a trap. She betrayed not just the Straw Hat Pirates but Sanji as well and was planning on killing him and his entire family.
He even fought against Captain Rocks on God Valley. Garp may be old right now, however, he is still more than capable of taking on Shanks in battle. This is evident from the fact that he recently set out to fight not just Blackbeard, but his entire crew on his own so as to rescue Koby from the grasp of the Yonko.
Shanks is actually a deep undercover government agent. When he had the fruit, he was taking it back to the government before Luffy ate it. He didn't kill Luffy immediately because he liked him or some other anime reason, but at the end of the anime he gets betrayed.
Mihawk holds the title of "World's Greatest Swordsman" and, as such, it is beyond any doubt that his swordsmanship skills are superior to those of Shanks. This was, once again, brought up in One Piece 1058 where he was specifically compared to Shanks.
Zoro set out on his journey to becoming the greatest swordsman in the world by defeating Dracule Mihawk, the man who currently sits on the stone. 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.
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.
Chapter #1067 of One Piece teases that the long-awaited first meeting between Luffy and his father Dragon is actually going to happen very soon. The highly anticipated meeting between Luffy and his father Dragon could be happening sooner than One Piece fans expected.
1) Kaido. Kaido did in fact lose to Luffy's Gear 5 at the end of the Wano Country arc. However, keep in mind that he withstood multiple waves of strong enemies before this final encounter. Luffy was also completely worn out after the fight and fell into a coma for about a week.