One Piece: What Would Have Happened to the Straw Hats if They Never Met Luffy?

gamerant.com:

The Straw Hat Pirates are at the core of Eiichiro Oda's One Piece and the story follows their adventure all the way from the East Blue to the Final Island, Laugh Tale, and potentially even beyond. Luffy, the captain of the crew and the main character, is, undoubtedly, the most important person in the story and as he began his journeyed from Fushia Village, he amassed quite a powerful crew.

Gathering the likes of Zoro, Nami, Usopp and Sanji from the East Blue, the group headed into the Grand Line where they further recruited Chopper, Nico Robin, Franky, and Brook. Taking two years to get stronger, Luffy and the group set sail for the New World where they managed to get one of the former Shichibukai, Jinbe to join them. While all of the Straw Hats had a personality of their own before meeting Luffy, he certainly did have a profound effect on all of their lives.

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The start of Luffy's journey was a clear indication that he was, in fact, a person who brought everyone together. Right from the very beginning of the story, Luffy helped those he felt needed it and freed them from oppression and tyranny. As such, a character like him inevitably changed lives for the better. For instance, as soon as Luffy set off on his journey, he saved Koby from Alvida's tyranny and inspired him to chase his own dreams. Years later, Koby still holds Luffy in high regard despite being a direct rival to him. While Luffy has affected thousands of lives with time, he's touched the hearts of the Straw Hat Pirates the most.

In his own way, Luffy has affected the lives of every single member of the Straw Hat crew. He's given some a reason to fight and push forward, such as Nico Robin, and saved others from impending death,