There are countless clashes Luffy faces in the epic story it tells ONE PIECE, and many of them have left their mark on the protagonist's body. Scars are a distinctive feature of many characters in the series, but sometimes the author chooses to make them disappear, like the wound Luffy received during the fight with Katakuri.
The punchlines of the story arc set on Whole Cake Island, lands under the rule of Empress Big Mom, were marked by a spectacular fight between Luffy and Katakuri in the mirror world created by Charlotte Brulee through the powers of the mirror-mirror fruit. The two displayed their best techniques, without compromise, and prior to the debut of Snakeman, a special form of the Gear Fourth, Luffy was pierced by a piercing mochi from Katakuri.
The wound as shown in the Final table of chapter 892, almost made Luffy pass out, and as pointed out by user @Geo_AW in the post below, it should have left a large scar on the protagonist's left side. A curiosity that involved hundreds of enthusiasts willing to justify the absence of the scar as a factor simply related to too many Details continuously inserted by both Eiichiro Oda and the animators by Toei Animation.
There are also some fairly detailed illustrations in the comments of each scar left on Luffy by an antagonist of a given level. The most reasonable hypothesis regarding the absence of all these signs on the protagonist's body appears the lack of their diegetic weightas the huge X-shaped scar Akainu left on his chest and the cut under his left eye represent two extremely important moments in Luffy's life, the fight to save his brother Ace and the dare for the Shanks pirates.
Finally, remember that there is a lively discussion in the fandom about who is stronger between Zoro and Yamato, and we leave you with the bugs corrected in Volume 105 of ONE PIECE.
I still don't understand how Luffy didn't get a permanent scar from this pic.twitter.com/xAUiCgbTPr— Geo (@Geo_AW) March 12, 2023