Gonna make each of them a poll. In the beginning, there are gonna be 8 rounds. After that, there will come the quarter finals, the semi finals, and the finals. For each poll, the character with the most votes will win and move on to each stage, and it won't be in my opinion even if I strongly disagree.
The Rounds:
Round 1: Hancock vs Jinbe
Round 2: King vs Katakuri
Round 3: Lucci vs Queen
Round 4: Law vs Magellan
Round 5: Crocodile vs Beckman
Round 6: Zoro vs Marco
Round 7: Yamato vs Ace
Round 8: Sabo vs Sanji
P.S: The characters that are gonna be fighting each other in the rounds were actually chosen randomly (I used a spin wheel), so I expect the polls to go a bit unfair.