Yes, there are some. Some might explore an alternate universe where Natsu has an 'evil' side and his relationship with Juvia is reimagined in a very different and often dramatic way.
Well, Archive of Our Own is a great place to start. It has a large collection of fanfics from various fandoms. Just use the search function and type in 'evil natsu x juvia fanfic'. Also, FanFiction.net has been around for a long time and has a lot of content, so it's also worth checking there. Another option could be some dedicated Fairy Tail fanfic forums where fans might share their works, including this specific type of fanfic.
They are popular because it's an interesting pairing. Natsu is a powerful and energetic character, while Juvia is emotional and passionate. Their personalities can create a lot of interesting interactions and storylines.
I'm not entirely sure specifically as it could be a very fan - created concept. But generally, if it's a fanfic involving Natsu and Juvia, it might be about their relationship in a new, fictional scenario created by the fan writer. It could include adventures they go on together, or perhaps how their personalities interact in different situations.
One great 'natsu x juvia fanfiction' is 'A Chance Encounter'. It beautifully portrays their relationship development in a unique magical world setting. The author does an amazing job of showing Juvia's shy yet determined love for Natsu.
There are so many fanfictions out there, and it can be a bit of a hunt to find a great 'Juvia x Natsu pregnancy fanfiction'. Some things to keep in mind are the writing style of the author. If you prefer more descriptive and emotional writing, look for stories that are praised for their prose. Also, check if the plot makes sense within the context of the 'Fairy Tail' universe, since Juvia and Natsu are characters from it. It might take some time to sift through, but with a bit of patience, you could find a really interesting one.
One good natsu x juvia fanfic could be 'A Chance Encounter'. It focuses on how Natsu and Juvia's relationship might develop in an alternate universe where they meet under different circumstances. For example, they might be on a joint mission and slowly realize their feelings for each other.
Well, it depends on the author's imagination. Maybe Natsu's raw power would give him an edge initially, but Juvia's strategic use of water could turn the tables. It could lead to a thrilling back-and-forth.
One reason is the contrast between their personalities. Juvia is often shy and reserved in her own way, while Natsu is bold and brash. The idea of these two coming together creates an interesting dynamic that fans like to explore in fanfiction.