One possible plot could be that our man discovers a hidden power within himself that no one else has. He uses this power to turn the tide in the final battle against the Titans. Maybe he can communicate with the Titans in a unique way and convince some of them to stop attacking, thus changing the whole scenario of the final fight.
Well, perhaps 'our man' in the 'attack on titan final our man fanfiction' is an ordinary soldier who was thought to be unremarkable at first. But during the final events, he stumbles upon an ancient relic that gives him the ability to control time briefly. He uses this power strategically in battles against Titans, saving his comrades and making crucial moves that lead to victory. He also has to deal with the moral implications of using such a powerful and potentially dangerous ability.
He could be a long - lost relative of one of the main characters. For example, he could be Eren's long - lost cousin. He has been living in isolation all this time, but now he emerges during the final events with some unique abilities or knowledge that he inherited from his family's side, which could play a major role in the fight against the Titans.
A great plot for such a fanfic could be that Mikasa's Titan form is a result of a connection to an ancient Titan power. As she becomes a Titan, she starts to have visions of the past, of how the Titans came to be. She then decides to use this knowledge and her new form to try and end the Titan - human conflict once and for all. Along the way, she has to face her friends who are initially scared of her but eventually come to accept her new form as she proves that she is still the same Mikasa deep down, just in a different body.
Well, perhaps she is reborn as a member of a noble family in the Attack on Titan world. This gives her access to resources and influence. She could use this new - found power to reform the military or start research into alternative ways to deal with the Titans. She might also get involved in the complex political web within the walls, trying to bring about peace and unity among the different factions.
One possible plot could be that Naruto and his friends somehow end up in the world of Attack on Titan. Naruto's ninja skills would be really useful against the Titans. For example, his shadow clone jutsu could be used to distract the Titans while the Survey Corps tries to attack their weak points. Also, Sasuke's sharingan might be able to see some hidden details about the Titans that the people in the Attack on Titan world don't know. It would be an epic adventure as they combine their powers to fight the common enemy - the Titans.
Well, it could be about Sephiroth using his incredible combat skills from Final Fantasy in the world of Attack on Titan. Maybe he teams up with the Survey Corps to take on the Titans. He might use his Masamune sword to slice through the Titans' nape with ease, bringing a new level of badassery to the fight against the Titans.
Perhaps Eren and his friends from Attack on Titan enter the Unordinary universe and are mistaken for having abilities. They then have to navigate the complex social hierarchy of the Unordinary world while also trying to find a way back to their own world. And the Titans might start showing up in the Unordinary world, causing chaos.
One possible plot could be that the Titans somehow cross into Spider - Man's universe. Spider - Man initially mistakes them for some new kind of giant robots or mutants. He tries to fight them using his web - slinging and acrobatic skills. But he quickly realizes they are much more difficult to defeat as they keep regenerating. Meanwhile, some of the Survey Corps members from Attack on Titan also cross over. They team up with Spider - Man, teaching him about the Titans' weak points at the back of their necks. Together, they fight to keep both universes safe from the Titans.
One possible plot could be that the ponies accidentally end up in the Attack on Titan world through some sort of magical portal. They then have to figure out how to survive in this harsh environment. They could use their unique pony abilities, like Fluttershy's connection with animals, to try and understand the Titans better. Maybe they could even find a way to communicate with the Titans and find out if there's a way to stop the attacks without all the bloodshed.
One possible plot could be that the Avengers are somehow transported to the world of Attack on Titan. They team up with the Survey Corps to fight the Titans. Iron Man could use his high - tech suits to take on the Titans from a distance, while Captain America leads the ground troops along with Eren and his friends. Thor could use his lightning powers to stun the Titans, making it easier for the others to attack.
One possible plot could be that Naruto and his friends are transported to the world of Attack on Titan. Naruto's ability to use chakra and his ninja skills could be used to fight the Titans in a unique way. For example, he could use his Shadow Clone Jutsu to create multiple clones to distract the Titans while the Survey Corps tries to attack their weak points. His Rasengan could also be a powerful weapon against the Titans' tough skin.