On a more magical level, reviving the dead is against the natural order of things in the wizarding world. This could attract unwanted attention from magical authorities or even dark forces. Some might see Harry's act as a dangerous precedent and try to either stop him or use his new - found power for their own evil purposes.
In some fanfictions, Harry might use extremely powerful and ancient magic. Maybe he discovers a long - lost spell during his adventures that has the power to reverse death. For example, he could find a spell hidden in a forgotten corner of the Hogwarts library that was created by a powerful wizard in the past but was deemed too dangerous to be used.
On a personal level, Naruto would finally get the family he always wanted. But it might also bring some confusion and adjustment issues. His parents would be from a different time, and they'd need to adapt to the new world Naruto lives in. For example, they might be shocked by the new technology and the changes in ninja warfare.
Perhaps in the fanfiction, Goku's love for his parents is so strong that it creates a new type of energy. This energy is noticed by a powerful and benevolent entity who offers Goku a deal. If Goku can prove that he will use his power for good and protect the universe even better with his parents alive, then he can revive them. Goku then has to go on a journey to show his worthiness, facing off against old and new enemies along the way.
It could be possible in fanfiction. Maybe Goku discovers a new type of wish - granting magic that is even more powerful than the Dragon Balls. Or perhaps he travels to a different dimension where time and death work differently. Fanfiction allows for creative interpretations. But in the official Dragon Ball story, there's no indication that such a thing could occur. The Saiyan race has its own limitations and the concept of death is pretty well - established in the series.
One consequence could be a change in the family dynamic. His mom would be back, and Naruto would finally have the family he always dreamed of. This might also have an impact on his relationship with his dad, as they would all be together again.
One way could be through some powerful forbidden jutsu. Maybe he discovers a long - lost scroll that contains a jutsu specifically designed to bring back the dead. However, such a jutsu would likely come with a great cost, like sacrificing a large amount of his own chakra or even his life - force.
Yes, there might be some extremely dark and out - of - canon fanfictions out there with such a disturbing premise, but it goes against the general nature of the original story where Harry's parents loved him deeply. However, in the vast world of fanfiction, people can create all kinds of strange and often inappropriate scenarios.
One possible reason could be that he might feel abandoned. Growing up without them, he could resent the fact that they left him an orphan. He might think that if they were really so great, they would have found a way to survive and be there for him.
One possible reason could be a misunderstanding. Maybe he discovers some secrets about his parents that he misinterprets. For example, if he finds out they were involved in some dangerous or morally ambiguous activities in their youth that he doesn't fully understand at first.
One possible reason could be that he discovers some long - hidden family secrets that make him question his parents' actions or decisions. Maybe he finds out about some dark deeds in their past that he can't overlook.