It might also be about how Naruto is treated or perceived in the fanfiction. If the other characters see him as a monster, either out of fear of his power or because of some misinformation or plot device, then that would create the feeling. This could lead to interesting storylines where Naruto has to deal with being ostracized or hunted because of this false perception of him being a monster.
Another way could be in the way his powers affect him. Maybe the use of his powers starts to corrupt him physically or mentally. His eyes could turn into some sort of inhuman or demonic - looking form, and his mind could be filled with uncontrollable rage and bloodlust every time he taps into his power, making him seem like a monster.
In fanfiction, 'Harry Potter feels numb' could imply that he's in a state of shock or emotional overload. Maybe he's been through a particularly traumatic event, like seeing a loved one die or experiencing a great betrayal. This numbness could be his mind's way of protecting itself from the full brunt of the pain.
Well, Stephen King novels are known for their horror and suspense elements. So if your life feels like one, perhaps there are things that scare you or keep you on edge. It could be that you face challenges that seem as menacing as the monsters in his books. Maybe there are secrets or hidden threats in your life that you're only gradually becoming aware of, much like the characters in King's novels who often find out about the true horror bit by bit.
Well, 'Harry Potter is a monster fanfiction' might imply that someone has written a fanfiction in which Harry Potter has some sort of connection or transformation into a monster - like being. It could be a really out - there take on the character, where his normal wizarding self takes on some monstrous traits, perhaps due to a dark magic spell or some strange encounter. This type of fanfiction might explore new and darker aspects of the Harry Potter world that weren't fully explored in the original series.
It could feel sweet and charming. The interaction between the gumball and Penny in the fanfic might bring out a sense of fun and adventure.
He might focus on his training. By pouring his energy into getting stronger, he can distract himself from his lonely feelings. Naruto has always been determined, and training gives him a sense of purpose.
In many fanfictions, Naruto might start by training harder. He throws himself into his ninja training as a way to distract himself from the loneliness. It gives him a sense of purpose and also helps him become stronger.
It would be quite an interesting sight. Naruto's energetic and passionate personality might bring a unique flavor to the song. His strong voice, which we usually hear shouting out jutsu names, could be adapted to singing in a really engaging way.
It could imply that there is a fanfiction where Harry Potter is depicted as an unstoppable monster in some way, perhaps with new and unexpected powers or a dark and menacing nature that defies the normal characteristics we associate with him.
There may be such fanfictions in some corners of the internet, but they are not representative of the overall Naruto fan community. Most fans are more interested in the positive aspects of Naruto's story, like his journey to become a great ninja, his relationships with his friends and mentors. Such inappropriate content is more of an outlier.