The other characters' development would be completely derailed. For example, Chopper, who looked up to Luffy as a source of inspiration, would probably lose his confidence. Robin, who had found a new family in the Straw Hats with Luffy as the core, might isolate herself again. Without Luffy, the bonds that held the crew together would start to crumble, and their individual character growth would be stunted.
Well, Neville would also be affected. Harry was an inspiration to Neville, and without him, Neville might struggle more with his confidence. However, it could also be a turning point for Neville, where he has to find his own inner strength without Harry's example. Ginny would be heartbroken. She had a special connection with Harry. Her character might become more reserved and less outgoing as she deals with the loss. For the Hogwarts professors, they would have to deal with the loss of a student in a different way. McGonagall, for example, would be deeply saddened and might become more protective of the remaining students. Snape would have a different emotional response as well, as his complex relationship with Harry was a big part of his character development.
The impact would be huge. First, the Straw Hat crew would be devastated. They would likely lose their motivation and purpose. Zoro might go on a vengeful spree. Also, the whole world of pirates would be shaken. Luffy was seen as a rising star, a symbol of hope for many. His death could lead to a power vacuum that other pirates would fight to fill.
Harry would be crushed. He'd feel like he lost a sister. Ron would be in total despair, probably blaming himself. Ginny would be heartbroken too as Hermione was like a sister to her. The Weasley family, who had accepted Hermione as one of their own, would be in mourning. They'd all wonder how they could have prevented it and would be angry at the unfairness of it all.
In the fanfiction, with Female Luffy, the relationship might have a different dynamic. Maybe there would be a more sister - like bond with Ace. She could be more empathetic towards Ace's past traumas compared to male Luffy. For example, when Ace talks about his father, Female Luffy might offer more emotional support.
Blackbeard's crew is also a diverse bunch. His more aggressive members like Burgess might be eager to start a fight with Luffy's crew. However, some of the more cunning members could be thinking of ways to use the situation to their advantage. They might try to manipulate Luffy or his crew into making mistakes. And if Blackbeard decides on a certain course of action, his crew would generally follow, but there could be some internal dissent depending on the situation.
Nami would probably be devastated. She has been with Luffy through so much, and his death would be a huge blow. She might become more withdrawn and serious, as Luffy was often the one to bring out her lighter side.
The characters would be devastated. Grover, Percy's best friend, would be heartbroken. He might lose his ability to find Pan because of the emotional turmoil. His search for Pan was always connected to his friendship with Percy, and without Percy, he could be lost.
In this fanfiction, Naruto might use his shadow clone jutsu to create distractions while he rescues Luffy and Ace. His speed and combat skills could prove crucial.
Sakura would be heartbroken. She would probably blame herself for not being able to protect Naruto. She might also start to train harder to fill the void left by Naruto.
Sakura would be devastated. She has been Naruto's teammate for a long time. She might blame herself for not being able to save Naruto. She would probably become more withdrawn and focus all her energy on finding a way to bring Naruto back, even if it's impossible. Kakashi would be deeply saddened too. He has always seen Naruto as a special student. He would likely feel that he has failed as a teacher.