He survives by using his quick thinking skills. Just like in his own world where he faces various threats, he can analyze situations in the Gundam Wing dimension and find ways to stay safe.
Harry might survive in Azkaban because of his connection to his friends, even if they betrayed him. Their memories could give him the strength to hold on. And he may be able to use his magic in unique ways. He could draw on the positive emotions he has left, like his love for his parents, to create a shield against the Dementors. Plus, he may be constantly looking for a way to prove his innocence and that hope could keep him alive.
In some fanfics, he might be saved by his latent magic power that suddenly bursts out when he is in extreme danger. For example, it could create a protective shield to fend off the Dursleys' attacks.
In some versions, Harry might be saved by his magical abilities emerging in a crucial moment. Maybe he uses magic to make food appear for himself, defying the Dursleys' cruel intentions.
Harry Potter could survive in the dungeon without his glasses by relying on his instincts. He has been in many dangerous situations before and has developed a good sense of danger. He could listen intently for any sounds that might indicate danger or a way out. Additionally, he could try to communicate with magical creatures in the dungeon. Some might be friendly and help him. And if there are any magical objects in the dungeon, he could potentially use them to his advantage. For instance, if there is a magical stone that enhances perception, he could use it to'see' better without his glasses.
Well, Vincent survives mainly because of his ability to adapt quickly to unexpected circumstances. Also, he has a certain level of street smarts that helps him avoid getting caught in fatal traps. Plus, maybe a bit of divine intervention or just the plot's design to keep him alive for the story to unfold.
Flash often uses his super speed and quick thinking to navigate through crises. His speed gives him the ability to react fast and find solutions that others might miss.
It can make readers view the original series as more fragile. Since Harry Potter is the main hero in the original, his death in fanfiction shows that the world J.K. Rowling created can be drastically altered.
In fanfiction, the tower could have some sort of magical protection or power that Lucy can use to her advantage against the dragon. Maybe there are magical symbols on the walls that she can activate to create a shield around herself. Or perhaps there is a special room that the dragon cannot enter. She can retreat to this room when she feels threatened. She could also try to tame the dragon over time. By showing kindness and not being a threat herself, the dragon may gradually become more friendly towards her and she can then survive more easily in the tower with it.