One possible fanfiction could be where Jon Snow stands up to the Night King directly. He might use his skills and knowledge of the enemy to taunt the Night King, saying that he will never succeed in his dark plans. This shows his courage and determination to protect the realm.
This theme can also explore the idea of self - discovery. As Jon stands up for himself, he might learn more about his own values and limits. In fanfiction, he could be in a situation where he has to choose between his loyalty to different groups. By standing up for himself, he figures out where his true loyalties lie. It's a journey of self - realization within the context of a fictional world.
One scenario could be in the Hogwarts corridors. Maybe some Slytherins are taunting Harry about being a half - blood. In the fanfiction, Harry decides he's had enough. He stands up straight, looks them in the eye, and firmly tells them that his blood status doesn't define him. He uses his skills in magic, like a well - executed non - verbal spell, to show he's not to be trifled with.
I would recommend 'Harry's Solitary Stand'. In this fanfiction, Harry finds himself isolated from his friends due to a misunderstanding. Instead of waiting for them to come around, he stands up for himself and his actions. He embarks on a solo adventure where he discovers new aspects of his magic and his own strength. It's a really interesting read as it shows Harry's growth outside of his usual support network.
One great 'Harry Potter stands up for himself' fanfiction is 'The Power Within'. In this story, Harry decides he's had enough of being pushed around by the Ministry and starts to take matters into his own hands. He uses his knowledge of magic in unexpected ways to fight against the unjust rules. Another is 'Harry's Rebellion' where he rebels against Snape's unfair treatment in Potions class and shows his true skills and confidence.
Ron and Hermione are the most likely. They've always been by Harry's side in the original series. In the fanfiction, when Harry stands up for himself, they would surely be there. Ron might use his sense of humor to diffuse the situation if it gets too tense, while Hermione would back Harry up with her vast knowledge of wizarding laws and rights.
Jon Snow could potentially have allies like the Mormonts. They have always been loyal to the Starks. Maybe even some of the Dornish houses might side with him. They have their own reasons to oppose the current power structure in Westeros. And of course, his friends from the Night's Watch who left with him or believe in his cause could be his allies in this conquest. He might also gain the support of some of the maesters who see the value in his leadership for the future of Westeros.
Daenerys Targaryen could be one to help. Since she has experience with dragons, she could give Jon Snow advice on how to care for the egg and hatch it.
It could be a young and untainted Frey. Maybe a niece or a cousin of the more infamous Freys. One who has not been involved in the past atrocities committed by her family and has a more noble heart.
Daenerys Targaryen is often paired with Jon Snow in such fanfictions. Their combined power and the potential for a different kind of relationship makes it a popular choice among writers. Another character is Arya Stark. Their sibling bond can be explored in new ways when Jon is reincarnated, like Arya helping Jon with her assassin skills in a different plot line.