Big Mom
Big Mom fights Luffy over food. Food, like sake or treasure for other Straw Hats is meant to represent Luffy’s inner desires and selfishness, Luffy fasts to bring back his friend while Big Mom’s selfishness destroys her allies.
The selflessness of Luffy and Sanji that was portrayed throughout the arc allows them to defeat her. Luffy surpasses Big Mom because a king doesn’t put his personal desires above the interests of his subjects like she did in Fishman Island and Whole Cake Island. Luffy doesn’t need to beat her in a fight to surpass her because he already did through Sanji’s cooking, a represention of his selflessnes. Big Mom was Luffy’s main thematic enemy in Whole Cake Island and not Katakuri. Whole Cake Island is an arc that focuses on the bond between Luffy and Sanji.
Kaido
Kaido represents peak strength and authority. King thought that as long as Kaido is the strongest he can become Joy Boy.
Kaido ruled Wano using strength and fear stealing the smiles of the people of Wano to create an army of devil fruit users. Yasuie notices that Zoro doesn’t smile or laugh even though smiling can bring you good fortune. Zoro became hyper serious after Thriller Bark when he took all of Luffy’s pain and realized that he needs to become much stronger to help him become the Pirate King. Zoro lends Luffy his strength in Wano to help him surpass the strongest creature and become Joy Boy. Luffy surpasses Kaido because a king doesn’t rule using an iron fist and tyranny, instead he is the one who can bring joy and laughter to his friends and subjects.
By the end of the Fire Festival, everyone in Wano including Zoro will laugh as hard as they can. Wano is an arc that focuses on the bond between Luffy and Zoro
Shanks
In many ways he is the opposite of Kaido. Kaido has a crew that tests the strongest and Shanks has a crew that exposes the weakest. Shanks recruited Yasopp because of his talents and Luffy recruited Ussop because of pure friendship, Shanks is the Emperor that represents friendship and he is the one who showed Luffy how a true friend acts, he and his crew are the strongest unit when they fight together.
Shanks has a crew that has no weak members and the weakest Straw Hat is the one that will allow Luffy to surpass Shanks and will turn the Straw Hats into the most solid well-rounded crew. Luffy will surpass Shanks in Elbaf by recruiting a crew that is better than his and by having friends better than his. Elbaf is an arc that focuses on the bond between Luffy and Ussop.
Blackbeard
Why did Oda separate Lodestar Island and Laugh Tale from each other and made them both very hard to reach islands instead of one single island at the end of the Grand Line like we initially thought, isn’t it redundant? If Kaido epitomises the battle shounen aspect of the series through his unparalleled sheer strength then Blackbeard is the main antagonist of One Piece, an adventure series about a boy looking for a treasure.
Blackbeard doesn’t care about Lodestar Island just like he didn’t care about visiting Skypiea, his only concern is reaching an end goal by any possible means, that is to reach Laugh Tale through the Poneglyphs. But for Luffy and Nami, Lodestar Island means everything to their dreams, for Nami to chart a map of the World and for Luffy to have a complete adventure and become the freest man in the seas.
While Lafitte, the navigator of the Blackbeard Pirates was busy infiltrating Mary Geoise to make Blackbeard a Warlord, Nami was busy trying to find a way to the Sky Islands. Just like how we now understand that Skypiea is very important for the end of the story lore, Crocus and Inuarashi told us that Lodestar Island is an important destination to reach. These 2 islands appear like side quests but they represent core of the series, adventure. The Roger Pirates reached Lodestar Island before finding the Poneglyphs but Blackbeard will never reach Lodestar Island.
Roger became the King of Pirates because he conquered the Grand Line and ruled every sea and island, not because of some powerful weapon or asset. And Luffy will become the Pirate King after Nami takes him to the Lodestar Island and Laugh Tale. Blackbeard chases an endgoal while Luffy and Nami’s adventure has no end. Laugh Tale is an arc that focuses on the bond between Luffy and Nami.
*by ThrowawayOpAcc0618
