ZORO VS FUJITORA: This fight was anticipated in Dressrosa, where Zoro and Issho clashed. Zoro defeating Fujitora in a duel would be a remarkable feat to add to his resume.
SANJI VS KIZARU: Sanji vs. Kizaru is a pretty expected fight by fans. Both use kick attacks, Sanji exclusively uses them while Kizaru’s strongest attacks are kick attacks. Sanji specializes in Observation Haki, Kizaru is the fastest, to the point where you cannot even react to him. This fight will probably happen near the end of the series, if so, Sanji’s Observation Haki will probably be at its peak, probably fast enough to react to Kizaru by then.
MONKEY D. LUFFY VS AKAINU: Luffy’s revenge for Ace’s death. Maybe he will take his revenge with the help of his brother Sabo.
SABO VS AKAINU: Ace fought Akainu for Whitebeard’s honor and eventually sacrificed his life for his little brother- Luffy. Sabo could fight Akainu in order to save Luffy, however, this time he wouldn’t die.
SUPERNOVAS TRIO VS KAIDO: As we have seen recently, the gap between Luffy and the Yonkos seems to be a bit larger than what some people may have expected.
Kaido doesn’t appear to be the sort of enemy Luffy can defeat 1v1. Luffy may inflict the deciding blow thanks to his Advanced Armament Haki but surely he will need help from Eustass Kid and Trafalgar Law.
SHANKS VS BLACKBEARD: This fight has been hinted a lot. Those Shanks’ scars, Shanks’ concern about Blackbeard’s rising strength, Blackbeard outright saying at the end of the war it’s not the time for their fight implying there will be one.
MONKEY D. DRAGON VS BLACKBEARD: Blackbeard is currently targeting the Revolutionaries, but can he really defeat the most dangerous and most wanted man in the world?
ZORO VS MIHAWK: This fight has been hyped up since the beginning of the series. Mihawk is the current holder of the title, “Greatest Swordsman in the World”. Because of his status, defeating him is Roronoa Zoro’s ultimate goal.
ZORO VS SHILIEW: Shiliew has eaten the Suke Suke no Mi which gives him the ability to turn himself and other things invisible. Its Awakening form could allow Shiliew to erase every trace of his presence.
In this case Zoro would be forced to push his Observation Haki to its peak to defeat Shiliew.
MONKEY D. LUFFY VS BLACKBEARD: The ultimate fight for the title of “Pirate King”. Blackbeard is the greatest rival of Luffy. He’ll certainly be his final obstacle at Raftel.