Another possible development is that Natsu could become more empathetic towards those with dark powers or pasts. Knowing that he has a dark side as END, he would understand the struggles of others better. This could lead to him reaching out to characters who were previously considered enemies or outcasts, creating new alliances and story arcs within the fanfiction world.
He could become more brooding. Instead of his usual carefree self, he might be burdened by the knowledge of his true nature as END.
Natsu might also develop a stronger sense of self - control. Since he knows he is END and the power he holds can be dangerous, he would work on controlling his impulses. For instance, when he gets angry, he would try not to let his END power take over completely. This would be a significant change from his more impulsive nature in the original series. He may also start to train harder to better understand and master his END abilities, which could lead to new power - ups and techniques in the fanfiction.
One possible plot development is that Natsu, as END, could be hunted by various magical organizations who see him as a threat. This would put him on the run and force his Fairy Tail friends to either protect him or try to stop him if they believe he's too dangerous. Another development could be that Natsu discovers new abilities related to END that give him an edge in battles but also come with a cost, like draining his life force or affecting his mental state.
Natsu could develop a more empathetic side. Knowing Zeref as his brother, he might start to understand the pain and loneliness that Zeref has endured. Zeref, on the other hand, could become more open and less isolated. He might find a new purpose in protecting Natsu and the Fairy Tail guild. For example, Zeref could start to use his powers for good instead of causing destruction.
One possible plot development could be that Natsu discovers a new and powerful magic during his return that gives him an edge in saving Fairy Tail. Maybe he finds a way to combine his Fire Dragon Slayer magic with some ancient magic he stumbles upon on his journey back.
In some fanfictions, when Natsu turns into END, there's often a huge power boost. This can lead to him facing off against stronger enemies that he couldn't before. For example, he might take on the most powerful dark mages single - handedly. His appearance also changes, usually becoming more menacing with features associated with END. This transformation can also cause some internal conflict within the Fairy Tail guild, as some members may be afraid of his new form.
Sure, in the 'Fairy Tail' universe, the concept of Natsu being END is quite fascinating. Fanfiction writers often take this idea and run with it. They might create stories where Natsu discovers his true nature as END more gradually, or they could write about how the other guild members react when they find out. It can also lead to stories that explore the origin of Natsu as END and how it ties into the overall lore of the 'Fairy Tail' world.
In some fanfictions where Natsu becomes END, it often leads to a power - up that is both amazing and terrifying. His physical appearance might change, with more demonic features. His power level could skyrocket, making him one of the most powerful beings in the Fairy Tail universe. He might struggle with the newfound darkness within him, as END represents a very powerful and potentially evil force. This could lead to interesting storylines where his friends in Fairy Tail have to find a way to bring back the Natsu they know while still dealing with the power of END that he now wields.
There are some great ones. Some focus on Natsu's growth and how he overcomes final challenges at the end of the Fairy Tail story. Others might explore his relationships in a more in - depth way as the story comes to a close. It really depends on what kind of story you're interested in. If you like action - packed endings, look for ones where Natsu is using his full power to save the day. If you prefer more character - driven stories, there are those that deal with his emotions and bonds with other characters at the end.
Natsu's character development in this fanfiction might involve him becoming more responsible. With his end form, he has greater power and with that comes the need to use it wisely. He could start to think more about the consequences of his actions. For example, he might not rush into battles as blindly as he used to. Also, his emotional growth could be a part of it. He could become more in tune with his feelings towards his friends, especially Lucy. His loyalty to the guild could also deepen as he realizes his new form can be a great asset to protect Fairy Tail.
One possible plot development could be how Natsu, as a girl, changes the dynamics within the Fairy Tail guild. Maybe she forms different relationships with the other members. For example, her friendship with Lucy might become more sisterly or there could be new romantic interests from other guild members who see her in a different light.
Lucy could be a main character. She was always close to Natsu in the original Fairy Tail. So when Natsu returns as an 'ex' and meets the guild again, she would likely play a big role in how he is received and in the development of the story.