In some scenarios, they might die heroically in a big battle against dark forces. For example, while protecting Hogwarts, they could be outnumbered by powerful dark wizards.
It could be that the Weasley family sacrifices themselves to save others. They are a very selfless family in the original series. So in this fanfiction, they might choose to give their lives to protect their friends, neighbors, or the whole wizarding community from a great danger like a powerful dark magic weapon.
In some fanfictions, Spiderman might die due to a miscalculation in his powers during the battle in Civil War. Maybe he tries to overextend himself to protect civilians or other heroes and gets caught in a cross - fire that his body can't withstand.
It would be a huge loss. The Weasley family is well - known and loved. Their deaths would cause great grief among their friends and allies. It might also lead to a decrease in morale among the good wizards.
One possible scenario could be that Naruto was severely injured in a battle, perhaps against a powerful new enemy. He was brought to the hospital, but his injuries were too grave to be healed, and he passed away surrounded by his friends and family, leaving everyone in deep sorrow.
One possible scenario could be that Luffy sacrifices himself to save his crew during a major battle against an extremely powerful enemy. He might use all his strength and energy to protect them, and in the end, it's too much for his body to handle.
Another scenario could be that Gohan contracts a deadly and incurable disease in the fanfiction world. Despite the efforts of his family and friends, including the use of any available advanced technology or magic, he succumbs to the illness, leaving everyone in mourning.
Perhaps Naruto is betrayed by someone he trusts deeply. This person leads him into a trap at the Valley of the End. Naruto, being caught off - guard, is fatally wounded. His death in this fanfiction could be a tragic end to his journey of becoming a great ninja and a symbol of how even the most powerful can be brought down by treachery.
Another scenario could be that Iron Man is poisoned or infected with a deadly alien virus. He tries to fight it off but eventually succumbs to it. His friends in the Avengers try their best to save him but are unable to. This would be a really tragic way for him to go, especially considering how much he has done for the team and the world.
One possible scenario could be that he's overpowered by a very strong enemy on the bridge. Maybe a new, extremely powerful villain shows up and Naruto, despite his best efforts, just can't hold his own against their unique jutsu or skills.
One possible scenario could be that Percy sacrifices himself to save Annabeth from a powerful and deadly monster. Maybe a huge and ancient sea creature that only Percy can hold off long enough for Annabeth to escape, but at the cost of his own life.
One possible scenario could be that Edward sacrifices himself to save Bella from a powerful new vampire threat. Another might be that he succumbs to an illness that vampires in this fanfic world are suddenly vulnerable to. Or perhaps he is killed in a battle against a group of werewolves gone rogue.