A good one often has well - developed characters. For example, Sabrina's protective nature should be shown in a believable way, like how she defends Ash from other powerful Pokemon trainers or dangerous situations. Also, the relationship between Ash and Sabrina should grow organically. It shouldn't feel forced.
You can try looking on fanfiction websites like FanFiction.net or Archive of Our Own. They usually have a large collection of Pokemon fanfictions, and you might be able to find the Ash x Protective Sabrina ones there.
Probably Poseidon, as he is Percy's father and has a vested interest in his son's well - being. Zeus might also be protective in some cases, despite their past differences, as Percy is a hero who often saves the world which benefits Zeus's realm as well.
Their shared experiences play a big role. They've been through so much together, like countless battles and adventures. Percy has seen Annabeth in tough situations and he knows how strong she is, but also how vulnerable. So he feels the need to protect her. For instance, they might have had a close call in a previous adventure where Annabeth was nearly killed, and that memory makes Percy extra vigilant.
Perhaps Anko has a personal connection to Naruto. Maybe she sees a bit of herself in him, like his determination in the face of difficulties, and this makes her feel a sense of kinship and thus the need to protect him.
Maybe Blaise sees something special in Harry. In fanfiction, it could be that Blaise admires Harry's courage or his unique abilities. He might feel a sense of kinship with Harry despite their differences.
In fanfictions, Paul is often protective of Bella because he might sense her vulnerability. Bella is usually portrayed as a delicate character in the face of the supernatural world, and Paul, with his strength, feels the need to safeguard her.
Well, in many fanfictions, Rosalie sees Bella as a part of the family. Since she values family, she wants to protect Bella from any harm. Also, she may have a sense of loyalty towards Edward, and protecting Bella is a way of showing that loyalty.
Well, in many fanfictions, the Avengers protect Peter by always having his back in battles. For example, Captain America might shield him from incoming attacks with his iconic shield. They also offer him guidance. Tony Stark could be constantly giving him advice on how to improve his suit and combat skills.