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.
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.
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.
SUPERNOVAS TRIO VS KAIDO: 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.