In many Fairy Tail fanfictions, the battle between Natsu and Acnologia is often depicted as extremely epic. Natsu's fiery determination and his unique dragon - slayer magic make for an interesting contrast against Acnologia's overwhelming power. Some fanfictions might have Natsu discover new forms or powers in order to stand a chance against the fearsome Acnologia.
Some fanfictions to check out are 'The Dragon Slayers' Bond'. It really plays on their status as dragon slayers and how that common ground can bring them closer. There are a lot of sweet and tender moments in this one. 'Fire and Metal' is another one. It's set during a time when the guild is in danger, and Natsu and Gajeel have to work together closely. Their relationship blossoms as they fight side by side. 'Natsu, Gajeel and the Unspoken Feelings' is also a fan favorite, as it delves into the unsaid emotions between them that they're not quite sure how to handle.
You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just type in 'Fairy Tail Natsu Gajeel yaoi' in the search bar, and a bunch of relevant stories should pop up.
One possible plot could be that there is some sort of misunderstanding or dark magic at play that causes Natsu and Mavis to fight. Natsu, being hot - headed, jumps into the fray without fully understanding the situation. Mavis, on the other hand, is trying to figure out a way to stop the fight without harming Natsu. As the battle progresses, they both start to realize that they are being manipulated and then team up to face the real enemy.
Well, in such a fanfiction, Gajeel would bring a whole new energy. He might be more rebellious as a youngster. His journey to find his place in Fairy Tail could involve getting into small scuffles with other members at first. But as time passes, he realizes that Fairy Tail is a place where he can belong. His growth could be shown through his changing attitude towards the guild's rules and values.
One aspect that could be explored in this fanfiction is Gajeel's growth in magic. As a kid joining Fairy Tail, he would be exposed to different types of magic and training methods. Maybe he starts off with his Iron Dragon Slayer magic being quite basic, and then with the help of the guild's masters and other members, he refines it. He could also learn new skills that complement his existing magic, which would not only make him stronger but also show his development within the guild.
In a fight between Natsu and Mavis in a fanfiction, it's really hard to say who would win. Natsu is extremely powerful with his dragon slayer magic, being able to take on some really tough foes. However, Mavis is the first master of Fairy Tail and has a great deal of wisdom and powerful magic herself. It could really go either way depending on how the fanfiction writer wants to portray the battle.
Perhaps the Fairy Tail members watching will have different reactions. Some might be worried for Natsu, especially those who are close to him like Lucy or Happy. Others, like Erza, might be more focused on analyzing Natsu's moves and Zero's counter - attacks. And there could be some comic relief from the likes of Gray, making snarky comments while still being engaged in the fight between Natsu and Zero.
One exciting moment could be when Natsu first unleashes his most powerful Fire Dragon Slayer attack against Laxus. The sheer power of the flames and the look of determination on Natsu's face would be thrilling. Another moment might be when Laxus counters with his Lightning Dragon Slayer magic, creating a spectacular display of light and energy as the two elements collide.