Given the limited information, we can only assume that the strong boy is a key character. There could be other characters involved such as witnesses to the event of the throat being lifted. Maybe there was a victim whose throat was lifted, and depending on the context of the story, there could be adults or other children who play important roles in the aftermath of this incident.
I'm not sure specifically what this 'throat lifted by a strong boy story' is about as the description is rather unclear. It could potentially be a story about an incident where a strong boy somehow lifted someone by the throat in a fight or an accident perhaps.
Well, perhaps the strong boy was showing off his strength. He might have been a young athlete in training. The man could be his father or an older friend. The boy just got excited and decided to lift the man up, much to everyone's surprise.
He would gain Thor - like powers. Just as Thor can control lightning and has super strength, Harry might be able to access similar powers. He could use the hammer to fly and fight against enemies in a more powerful way than he could with just his wand.
It could be because some fanfiction writers want to take a different approach and create a new storyline where Harry's role or perception is challenged.
In addition to the trio, there could be characters like Draco Malfoy. He might be even more antagonistic towards Harry if he is seen as the 'Snake Boy', either out of jealousy or fear. Professor Snape could also play an important role. Given his own connection to the snake - like House of Slytherin, he might have some insights or conflicts regarding Harry's newfound snake - nature. And there could be some original characters created specifically for the fanfic who are also involved with Harry's snake - related adventures.
Obviously, the Head Boy himself is a very popular character. He is often depicted as strong - willed, intelligent, and with a sense of justice. Harry Potter might also be a popular character as he could interact with the Head Boy in various ways, like giving advice or getting involved in some adventures together.
Draco Malfoy is a very typical 'bad boy' in Harry Potter fanfiction. In the original series, he was a bit of a bully, and in fanfiction, this is often exaggerated. He can be portrayed as a brooding, conflicted character who might have a change of heart later. Another one is Sirius Black. His rebellious nature in the books makes him a prime candidate for fanfiction to expand on his 'bad boy' qualities, like his disregard for some of the more traditional pure - blood family values.
Sometimes, in fanfiction, authors like to challenge the established norms to create unique and unexpected plots. Maybe they thought it would add more depth or drama to have Harry Potter not be the boy who lived in their particular story.
Maybe it's a twist to explore Neville's potential and show a different outcome. It could be that the author wanted to give him a chance to shine and be the hero instead of Harry.