One challenge could be readjusting to the village life. After intense training in a different environment, the daily routines and social norms of Konoha might seem strange. Also, he may face jealousy from some of his peers who haven't advanced as much in their skills during his absence. Another challenge could be dealing with the new threats that Konoha might be facing, and having to prove himself all over again to the village elders that his new skills are useful for the village's protection.
In some fanfictions, Naruto might return to Konoha to a cold reception because the villagers still hold grudges from his past. Maybe they haven't fully accepted his power or the chaos he sometimes brought. For example, they could be afraid of his Nine - Tails power flaring up again and causing destruction.
Some villagers might be in awe of his new strength and abilities. They could see him as a great protector now. However, there may also be those who are still skeptical or even afraid because of his past as the container of the Nine - Tails. His friends would likely be overjoyed to see him back and eager to train with him or learn from him.
It could be a rogue ninja who has been secretly building power while Naruto was away. This rogue ninja might have a vendetta against Konoha and sees Naruto's return as a challenge to his plans. So he directly confronts Naruto to prove his own strength.
The fanfiction could focus on Naruto's married life in Konoha. Maybe his wife is a powerful ninja in her own right. Together, they could train the next generation of Konoha ninjas. Their relationship could be a source of inspiration for the young ninjas. Naruto's return with his wife could also bring new diplomatic relations to Konoha if his wife has connections to other villages.
Well, one possibility is that Naruto's son is very powerful and has unique abilities. When they return to Konoha, the villagers are both amazed and a bit worried about this new generation of power. Naruto might have to deal with the elders who are cautious about his son's potential. And his son could start making friends quickly with the kids in Konoha, like Boruto did in the original series.
It's possible that the child is an orphan Naruto found. Naruto, having known the pain of being alone as a child, decides to take the orphan under his wing. He brings the child back to Konoha to give it a home and a family within the village.
In this fanfiction, perhaps the child is Naruto's own. Maybe he had an adventure away from Konoha and met someone special. The child could be a symbol of his growth and newfound family. He returns to Konoha with the child to introduce it to his friends and show how he has changed.
In this fanfiction, the Naruto family might be welcomed back with great joy. The villagers could hold a big celebration to honor their return. Naruto, as a hero, would finally be home with his family in Konoha, and his kids might start exploring the village that their father has so many memories of.
Well, it could be that Naruto has found a way to tap into some ancient and forgotten power source during his time away. So when he comes back to Konoha, he's not only physically stronger but also has a deeper understanding of chakra and how to manipulate it. He might start by showing off his new skills to his old friends like Sasuke and Sakura. And then, he uses his strength to improve Konoha's defenses, such as creating new barriers around the village using his enhanced chakra control.