Another scenario could be that Tony is targeted by a powerful and vengeful enemy. The enemy manages to get the upper hand in a fight and mortally wounds him. His death then serves as a catalyst for the team to go on a full - throttle hunt for the killer.
In some fanfictions, Tony might die from an unexpected illness that the team discovers too late. His death could then lead to the team members reflecting on their relationships with him and how much he meant to them. For example, Gibbs might feel a deep sense of regret for not spending more time with him outside of work.
One possible scenario could be that Tony sacrifices himself to save a teammate during a dangerous mission. Maybe he takes on a bomb - defusing task and runs out of time, dying heroically.
One possible scenario could be that Tony is in Siberia on a mission gone wrong. Maybe he's facing a powerful enemy there, and despite his best efforts, he gets fatally injured in a fight. Another could be that the harsh Siberian environment plays a role, like he gets caught in a blizzard and succumbs to the extreme cold.
Another theme could be the exploration of grief. When Tony dies, the other characters have to deal with their emotions. This can range from anger at the situation, to deep sadness and a feeling of emptiness. Fanfictions often focus on how each character copes differently, like Gibbs might become more withdrawn and focused on finding out what really happened, while Ziva might be more vocal about her grief.
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.
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.
In some fanfictions, Tony first meets Ziva at a party. He is drawn to her because of her mysterious aura. Ziva, on the other hand, is initially guarded. As they start talking, they discover they have different views on various topics, like music or food. This simple conversation starts the journey of their relationship, with both of them being curious about each other despite their differences.
One possible scenario could be that Edward sacrifices himself to defeat a powerful and final enemy. He might use up all his alchemy knowledge and power in one last, desperate attempt to save the world, and his body just can't take the strain.
One possible scenario could be that they sacrifice themselves to save the village from an ultimate evil. They might combine their powers in a final, desperate move that exhausts them completely, leading to their deaths.
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.
Perhaps in the fanfiction, Naruto is betrayed during the battle. By someone he trusted, like a comrade who was secretly working for the enemy. This betrayal catches him off - guard, and he is severely injured. Unable to fully recover, he succumbs to his wounds during the fight.
One possible scenario could be that Percy is overpowered by the various monsters in Tartarus. Maybe the sheer number of foes like the giants or the more terrifying creatures there are too much for him to handle, leading to his death.