In some fanfictions, they might show Harry having dark powers through things like unexpected magical outbursts with a malevolent tinge. For example, he could accidentally use a spell that causes harm in a way that seems to draw on darker magic. However, in the original series, Harry is firmly on the side of light magic, so this is a departure in fanfiction.
Often, in these fanfictions, the discovery of a new, ancient and dark magic artifact can be a plot device. Harry might find this artifact and, as he tries to understand or control it, he starts to develop dark powers. Also, the idea of a prophecy misinterpreted can play a role. A prophecy that was thought to be about his heroism is actually about his fall to the dark side, leading him to explore and use dark powers.
In some fanfictions, Naruto might gain the ability to control energy like a laser beam which is an alien - like power. For example, he could shoot beams from his hands to defeat enemies.
If Naruto had Superman's powers in fanfiction, it would change everything. His village would be almost invincible. With Superman - like powers, Naruto could fly around and keep an eye on all the hidden villages, preventing any surprise attacks. His super strength could be used to rebuild the village in no time after any destruction. Also, his x - ray vision could be used for various things like finding hidden traps or enemies. The power dynamic in the ninja world would shift completely, and Naruto would become an even greater legend.
Dark Naruto's powers would likely bring a new level of chaos to the Justice League. His Nine - Tails chakra is extremely powerful. In the context of the Justice League, he could potentially use it to enhance his physical abilities to superhuman levels, like being able to move at incredible speeds or having super strength. His ability to manipulate chakra might also be seen as a form of energy manipulation, similar to some of the powers of the League members.
He could develop the ability to combine his chakra with Superman's powers. For example, he might be able to use his Rasengan while flying at super - speed. Or he could infuse his chakra into his heat vision to make it even more powerful.
Well, it would be a wild change. Naruto's original powers are based on chakra and his ninja techniques. With Raven's powers, he might not rely as much on chakra. His fighting strategy would be completely different. He could use Raven's power of creating portals to travel across long distances without using chakra - consuming jutsus. This would also allow him to surprise his enemies more often. And in terms of the overall plot, it could lead to new alliances and enemies. For instance, those who are after Raven's powers might now target Naruto.
Well, his powers could be adjusted to fit the High School DxD universe's rules. Maybe his shadow clones could be used in a more sneaky way, like spying on the devils or angels. And his Rasengan might have some new effects, like being able to disrupt the magic in that world.
Well, in some fanfictions, Percy might have the power of enhanced underwater communication. He could talk to not just regular sea creatures but also mythical ones that are usually hard to reach. For example, he might be able to have a full - fledged conversation with a kraken.
Well, he might have shown superhuman strength, like being able to break things that normal babies couldn't. Maybe he could also sense danger in an uncanny way, like a sixth sense.