Well, in this fanfiction, it could be that Akatsuki has a change of heart. Some members might realize that Naruto represents a hope for the ninja world in a different way than they initially thought. So they step in to save him when he's in a really tough situation, like being trapped in a powerful jutsu or surrounded by a large number of enemy ninjas. They use their own unique skills, like Kisame's water jutsu or Itachi's Sharingan abilities to fight off the threats.
Well, it could be that there's a plot device like an ancient artifact. This artifact might have the power to draw out and combine the Akatsuki powers. The Akatsuki members themselves might be tricked into contributing their powers to this artifact, and then the protagonist or an antagonist gets hold of it and gains all those combined powers. It's a common trope in fanfiction to use such magical or mysterious items to bring about extraordinary power combinations.
Pain would still be a likely candidate. His Rinnegan gives him a powerful and commanding presence. He has the ability to see the big picture and make strategic decisions for the group.
One of the most popular female characters in Akatsuki in fanfictions is Konan. Her unique paper - based abilities and her complex relationship with Nagato and Yahiko make her a fascinating subject. In many fanfictions, her backstory is explored more deeply, especially her time growing up in the war - torn land of Amegakure. Another popular one could be Karin. Her connection to Sasuke and her own powers as a sensor type ninja give a lot of room for fanfiction writers to create interesting storylines, like her dealing with her feelings for Sasuke while being involved with the Akatsuki.
Pain would be one of the most challenging. His Rinnegan gives him a wide range of powerful abilities like the Six Paths of Pain. Naruto would have to figure out how to counter each of those paths and find a way to reach the real Pain. Itachi is also tough. His Sharingan and genjutsu skills are top - notch. Naruto would need to break free from his genjutsu and then find a way to fight back against his fire - based attacks.
The Akatsuki members themselves would have mixed reactions. Some, like Itachi (if he were still alive in the fanfic), might see Naruto as a potential asset but also a threat to their long - term goals. Kisame might be amused by Naruto's presence and see him as a new source of entertainment. Meanwhile, the Leaf Village elders would be outraged. They would see Naruto as a traitor and start devising plans to either bring him back or eliminate him.
Naruto could use his shadow clone jutsu to play pranks. For instance, he could make clones that look like the Akatsuki members themselves and have them do really silly things like dance around in circles or sing out - of - tune. The real Akatsuki members would be really confused at first, thinking one of their comrades has gone crazy.
There are so many fanfiction stories out there, and 'akatsuki find a baby' is a unique enough idea that it could have been explored in various ways. For example, in some fanfictions, the baby could be a key to some hidden power or prophecy that the Akatsuki is interested in. Or perhaps the baby is from an enemy clan, and the Akatsuki has to decide what to do with it. To find the exact fanfiction you're looking for, you could try searching with specific keywords related to the Akatsuki members involved, or any other details you might remember about the story.
I'm not entirely sure as there could be many novels with 'Akatsuki' in the title. It might be about a group of characters called Akatsuki in a fictional story. Maybe it involves their adventures, relationships, or a quest they are on.