I'm not sure it works with the movie and chapter 0 but in my head Shanks beating Shiki has always been the best route. Ex-Rocks splitting up the seas between them.
#1 WB
#2 Shiki
#3 BM
#4 Kaido
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#5 Ochoku - Hachinosu
WB refused to rule, Shiki tried to get too smart, BM was building alliances and Kaido was building an army.
Then WB got old, Shiki lost to Shanks, BM knew she wasn't strong enough and then made a fool of and Kaido lost just as he had built enough strength for his war.