Well, in some fanfictions, the plot revolves around Acnologia's redemption. He might start to see the value in the world he once wanted to destroy. This could be due to a series of events that make him realize there's more to life than just being a force of destruction. Also, a common plot is his relationship with other dragon slayers. Some fanfics explore how he interacts with them, whether it's a rivalry or an unexpected alliance.
Another plot might involve a prophecy. There could be an ancient prophecy that foretells the death of Acnologia at the hands of a new, unexpected hero. This hero could be a young mage who has been training in secret and has a special power that can counter Acnologia's strength. In the fanfiction, the journey of this hero towards fulfilling the prophecy and finally defeating Acnologia would be interesting to read.
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.
A common plot in Naruto vs Fairy Tail fanfiction is the power - exchange or power - up concept. For instance, a Fairy Tail wizard might gain some of Naruto's chakra - based abilities and use them in a new and interesting way. Or Naruto could learn some magic from Fairy Tail. Also, there are plots centered around a love interest between characters from the two universes. This can create a lot of drama and conflict as they come from different worlds with different values and cultures. Additionally, some fanfictions explore what would happen if the main villains from both series joined forces and how the heroes from Naruto and Fairy Tail would deal with it.
Perhaps a plot twist could be that the reincarnation as Acnologia is not a complete one. The character might start to transform into a hybrid form that combines the features of their Fairy Tail self and Acnologia. This new form could have abilities that are completely unique and unheard of in the Fairy Tail universe. And as a result, both the Fairy Tail guild and the other powerful beings in the world view this new form with a mix of fear and hope, not knowing exactly what to expect from it.
Some writers characterize Acnologia as a misunderstood loner. They show that his actions of destruction are a result of his past traumas. Others might make him more of a power - hungry villain who just wants to rule over all. There are also those who give him a sense of humor, which is a very different take from his usual brooding and menacing self in the original series.
A common theme in such fanfictions is Natsu's unwavering courage when facing Acnologia. He might not be as strong as Acnologia at first, but his will to protect his friends and the Fairy Tail guild drives him forward. His dragon - slayer magic could potentially have some hidden aspects that are only revealed during this encounter.
One exciting moment could be when Naruto first arrives in the Fairy Tail world and realizes the danger of Acnologia. His initial reaction and assessment of the situation would be thrilling. Another moment might be when he uses his signature jutsu against Acnologia for the first time, seeing how the dragon responds.
One possible plot could be that Acnologia, with his immense power, initially causes chaos within Fairy Tail. The members are both in awe and afraid of him. But as time passes, he starts to understand the concept of friendship and loyalty in Fairy Tail. He could then use his power to protect the guild from other major threats, like the Alvarez Empire. This would completely change the power dynamics in the Fairy Tail world.
One popular plot could be Erza having a moment of self - reflection during her shower. Maybe she's thinking about her past battles and how they've shaped her. Another could be a comical situation where her guild mates accidentally interrupt her shower, leading to some chaotic and funny interactions. It could also be a plot where she discovers a new magical ability while in the shower, perhaps related to the water or the solitude she finds there.
The guild as a whole would likely mobilize. Erza would start formulating a strategic plan. She'd consider the strengths and weaknesses of Acnologia and figure out the best way to approach the situation. Gray would also be ready to fight, using his ice - make magic to support the rescue mission. They would all be united in their determination to get Lucy back safely.