WARNING: The following contains spoilers for One Piece Chapter #1010 by Eiichiro Oda, Stephen Paul and Vanessa Satone, available in English now from Viz Media.
At the start of One Piece, Monkey D. Luffy endeared himself to fans as a loveably earnest kid who will do anything to protect his friends and crewmates. Regardless of how powerful or cruel the villain he came against was, Luffy approaches these fights with the same level of determination. When Luffy's adventure began, and even throughout recent arcs, he's often regarded as an underdog.
Still, as the Captain of the Straw Hat Pirates continues his journey toward becoming the King of Pirates, he's grown immensely. The current arc sees Luffy coming up against some of his most formidable opponents yet -- opponents who are so powerful that, if Luffy wins, it will be difficult to label him still an underdog. So, with a battle against the Yonko -- Kaido and Big Mom -- quickly gearing up, we have to look at how Luffy's likable underdog traits can still shine with his inevitable rise by the end of the Wano arc.
Luffy's status as an underdog is established early on, as he showcases his upbeat but reckless nature mixed with his roots of being from a small nowhere village. His only real possession was the straw hat given to him by his childhood hero, Shanks. Luffy's journey of becoming the King of Pirates sees him confront multiple adversaries, all of whom have been in the game much longer. On top of that, they rarely find Luffy to be any more of a threat than any previous rookie pirate they've seen before. This idea is perfectly represented when Sir Crocodile stabs Luffy through the chest, condescendingly remarking, "you're a two-bit greenhorn. Straw Hat Luffy, upstarts like you are a dime a dozen in the Grand Line."
Rookie pirates are constantly trying to make it into The Grand Line, and Luffy's undoubtedly not the first. Yet what makes him stand apart is his unwavering determination in the face of anyone who uses their power or authority to control or threaten the freedom of others. Combine that with the relationship he has with his Nakama, who are there to perform the tasks that Luffy himself can not, and you've got a bonafide shonen hero. So is Luffy in danger of not being our lovable underdog anymore? Well, yes and no.
Although Luffy's reputation and performance have steadily gone up with every arc, he's still as forward and gung-ho about adventure as when he first left Foosha Village. That part of him will never change. Still, if Luffy defeats Kaido and Big Mom, the world of One Piece can't look at him as a reckless upstart.
Underdog heroes are a big part of shonen, but typically, it is not as if they stay underdogs forever. Goku in Dragonball was a pint-sized ball of energy who his opponents constantly underestimated. Still, after the Frieza Arc, new adversaries like Dr. Gero and Cell were smart enough not to miscalculate fighting the fully grown Saiyan without a strategy in mind. Same with Yukihara Soma from Food Wars. After Soma and the rebels defeat Central in Food Wars and become The First Seat of Totsuki's Elite 10, Asahi Saiba does not make the same mistake in underestimating Soma that Azami did.
By that comparison, it's unlikely that Luffy can still be called an underdog if he defeats Kaido and Big Mom. They're just too big of names for people to brush aside his victory, and that's not even considering that the rubber man already has a bounty of a billion beli as well. Blackbeard and Fleet Admiral Akainu are the only two significant antagonists left for Luffy over the horizon. While they are both prideful, arrogant tyrants, it would be unwise for them to overlook a victory as world-shattering as this one.
There are countless examples of shonen heroes who begin their journey as underdogs and became legends in their respective stories. That's part of the charm of these types of stories. While characters like Naruto can no longer be considered underdogs, it's still how their journey began, and the characteristics that elevated them to persevere won't go away.
For now, we'll have to wait and see how Onigashima unfolds as Luffy is now taking on Kaido one-on-one. We've gradually seen this boy grow throughout One Piece, and no other fight has had this level of global repercussion since Enies Lobby and Marineford -- so becoming King of The Pirates seems now like only a stone's throw away.