It could also be an omniscient narrator. Adventure Time has a lot of different characters and complex storylines, so an omniscient narrator could tie all of Finn's story together, including things that Finn and Jake might not be aware of, like the backstories of the villains he faces or the hidden histories of the places he visits.
The 'Adventure Time Finn True Story' is likely about Finn's real adventures in the Land of Ooo. It could involve his battles, his friendships with Jake and other characters, and his journey of growing up in that magical and often dangerous world.
The Fire Kingdom's Flame Princess could be an ally too. Her mastery over fire could complement Finn's powers in combat situations. Also, the various magical creatures in Ooo, like the gnomes or the fairies, could band together and support Finn. They might have their own ancient knowledge or magic that could be useful to Finn in his adventures with his godlike powers. Finn's kindness towards them in the past might make them more inclined to help him out.
Well, Finn's real story is that he's a hero in the Land of Ooo. He's constantly on the move, exploring different parts of the land. He was raised in a rather unique environment, which has made him brave and curious. Finn has this unwavering sense of justice. For example, he'll always stand up to bullies like the Lich. His relationship with Jake is a big part of his story too. They're like brothers, always having each other's backs in any dangerous situation that they encounter during their adventures.
He might meet some of the more reclusive characters in Ooo that we don't usually see in the show. Maybe a hermit - like wizard who gives him some cryptic advice.
In Adventure Time, Finn's love story is quite complex. He has strong feelings for Princess Bubblegum. Finn's love for her is pure and often drives his actions. For example, he would go on many adventures to protect her kingdom. However, their relationship also has its challenges, like when Bubblegum's responsibilities as a princess sometimes come between them.
I'm not sure who the absolute best is, but some popular ones might be those who have a deep understanding of the Adventure Time universe. Writers who can capture Finn's adventurous spirit and Bear's unique personality well are usually great. For example, some authors on big fanfiction platforms who have a lot of positive reviews for their Adventure Time related works could be considered good authors.
The Lich could be a great antagonist. He might frame Finn as part of his plan to spread chaos and death in Ooo. Since the Lich is always looking for ways to disrupt the peace, using Finn as a scapegoat would be a clever move for him.
Well, in fanfics regarding Finn's arm in Adventure Time, some might focus on a magical or mythical origin for his arm. For example, it could be revealed that his arm has a connection to some ancient power or being from the Land of Ooo. It could also be used as a plot device to show Finn's growth. If his arm is injured, he might have to learn to adapt and become stronger in other ways, which would be an interesting character development arc in the fanfic.
One idea for an Adventure Time Finn arm fanfic could be that Finn discovers his arm has the ability to phase through solid objects. This new power could lead him on a quest to find out where it came from and how to control it. He might have to visit some of the more mysterious places in Ooo, like the Crystal Dimension, to get answers.
One aspect of 'Adventure Time Finn Alone Fanfiction' could be exploring Finn's character development in isolation. Finn is usually a very social character in the main series, so seeing him alone can show a different side of his personality, like his self - reliance and how he copes with solitude.