Itachi could be the most challenging. He's not only extremely powerful with his Sharingan and genjutsu skills, but he's also very intelligent. He could outwit Naruto in battle and has the ability to use Amaterasu, which is a very dangerous jutsu. Naruto would have to be on top of his game both mentally and physically to defeat him.
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.
Itachi could be a likely candidate. He has always had a complex relationship with Naruto. He knows Naruto's potential and his importance in Sasuke's life. Itachi might see Naruto as a key to changing the Akatsuki from within. He could approach Naruto with his calm and mysterious demeanor, explaining to him the real goals of the Akatsuki that are hidden beneath their violent exterior.
Doc Ock could be the most challenging. His mechanical arms give him great strength and reach. He can attack from multiple directions at once, which would be hard for Peter to dodge. Also, Doc Ock is highly intelligent and could come up with complex battle strategies on the fly.
I think Hidan would be the most difficult. He was always so hot - headed as an adult. As a baby, he would probably be very fussy and hard to calm down. He might throw tantrums all the time and not listen to whoever is taking care of him.
Itachi. He's one of the more complex and morally gray members of the Akatsuki. If he saw that the female OC was in a situation that could potentially cause chaos or harm to the ninja world in a larger sense, he might initiate the rescue. He's also the type who might see some value in the OC that others don't.
Yes, there are several fanfictions with this concept. In these fanfictions, Naruto's character often undergoes significant changes as he joins the Akatsuki. His motives for joining can vary from seeking a different path to having been influenced by certain events or characters. It's an interesting twist on the original Naruto storyline.
Well, if Naruto were an Akatsuki member, the storyline could be really different. For one, he might be on a mission to capture the tailed beasts for different reasons than in the original story. Maybe he was misled or had some hidden agenda. His relationships with the other Akatsuki members would be complex. He'd have to deal with characters like Itachi and Kisame. Itachi might see Naruto as a threat to his plan to protect Sasuke. And Naruto would also bring his own unique fighting style and values to the Akatsuki, which could cause internal conflicts within the group.
Naruto as an Akatsuki member would probably develop a more calculating side to his personality. He'd need to plan his moves carefully, as one wrong step in the Akatsuki could mean death. He'd still have his core of kindness, but it might be hidden deeper. He might be more hesitant to show emotions like anger or sadness, as that could be seen as a weakness in the Akatsuki. His loyalty would also be a complex thing. While he might be loyal to certain ideals he still holds, his loyalty to the Akatsuki as an organization would be conditional and full of internal conflict.
Itachi would be the most interesting babysitter. He has a calm and collected demeanor. He could handle Naruto's naughtiness with ease. His intelligence would also help him in understanding Naruto's motives and actions. He might also share some of his own experiences with Naruto, which could be both educational and inspiring for Naruto.
His relationship with Sasuke would be extremely interesting. Instead of being rivals from different sides, they could become comrades within the Akatsuki. This would change the whole dynamic of their relationship, as they might now work together towards the Akatsuki's goals, at least for a while.