One possible fanfic plot could be that Eren has been planning this for a long time. He might gather intelligence about the Colossal Titan's weaknesses. Then, in a fierce battle, he manages to get close enough to deliver a fatal blow. This could be a very emotional moment for him as well, considering the history between them.
Well, for one, the art styles could vary. Maybe the themes explored in each manga are distinct too. Also, the pacing and the way the story unfolds could be different.
Well, sometimes he uses his titan's speed and agility to dodge the Colossal Titan's attacks and then strike at its nape. It's a classic way to take down a titan in the Attack on Titan universe.
One common theme is loyalty. Given their roles in the story, fanfictions often explore how loyal they are to each other, whether it's in the face of danger or moral conflict. For example, in many stories, they will stick together no matter what decisions they have to make.
The theme of trust is crucial in 'Attack on Titan Reiner x Bertholdt fanfiction'. They have to trust each other completely in order to survive in the harsh world of Titans. Additionally, the theme of redemption sometimes shows up. If they make mistakes or have actions that they regret, they try to redeem themselves in the eyes of each other and also within the context of their friendship.
One popular 'Attack on Titan Bertholdt x Reiner fanfiction' is 'Beyond the Walls of Duty'. It delves deep into their complex relationship, exploring their shared experiences and the unspoken bond between them. The story often shows how they support each other during their difficult missions within the context of the 'Attack on Titan' world.
Another theme could be sacrifice. In the original story, both Bertholdt and Annie have to make difficult choices for the sake of their mission. Fanfictions might expand on this, showing how their relationship is tested by their need to sacrifice for their homeland. For example, a story could show Bertholdt's internal struggle between his feelings for Annie and his loyalty to Marley when he has to make a crucial decision. This can add a lot of emotional depth to their relationship.
I'm not sure about specific fanfictions off the top of my head, but you could also check out fanfiction.net. Some of the fanfictions might explore their relationship in depth, perhaps delving into their shared experiences as Warriors and how that affects their connection with each other. It's a great place to start exploring different takes on their relationship.
There's a fanfiction named 'Reiner and Bertholdt: A Different Path'. In this story, it takes a different turn from the original plot and focuses more on their relationship outside of the main battles. It shows their more personal side, like how they interact when they are alone. And 'Hidden Feelings' is also a good one. It delves into the emotions that Reiner and Bertholdt might have for each other but keep hidden from others.