Many Pirate Groups join or align themselves with the Pirate Group led by a Yonko. While Yonko himself in addition to having a large Group they still need alliances in order to enlarge the power of combat. Who are those who choose to break with the Big Mom Pirates? What is the reason?
1.jinbei
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Jinbei. A former Shichibukai also Former Vice-Captain of the Sea Pirate has the nickname of the Sea Knight. Because of the charisma of many fish humans who still follow it. He is allied with BMP to protect the Island of Fish Man. The arbitrariness of the Big Mom Government is very much against the principle. Bravery and courage Luffy confronts Big Mom inspires her to turn away from Big Mom and joins the Straw Hat Pirates (Ch.897).
2.germa 66
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Germa 66. Led by the Vinsmoke Family, mastered many advanced technologies devoted to war equipment, be it man-made to weapons. Although not yet officially allied with Big Mom Pirates. Their arrival to Whole Cake Island as well as approve of Sanji and Pudding matchmaking is a form that they are 90% ready allied. Big Mom's plan to finish and seize their technology, get them to abort the alliance and even revenge now turned against Big Mom Pirates for Sanji (897).
3.bege
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Capone Bege. Captain Firetank Pirates is a Big Mom's daughter-in-law. Behind the Alliance is a mask to overthrow or kill Big Mom in the future. On Sanji's wedding day she's allied with Luffy (her best friend) and betrayed Big Mom. He is currently with his wife and children group, in Yonko Big Mom's pursuit to give the Time of the Straw Hat Pirates (Ch.896).
so far that's all i know anyone who has resigned from younko alliance big mom even they have been planning how to beat big mom.