His ninjutsu might be enhanced. For example, his Rasengan could gain new properties due to the influence of Campione powers. His speed and strength, which were already considerable in the Naruto world, could be further increased. Maybe his ability to sense danger, which was related to his ninja training, could be upgraded to a more supernatural level in the Campione world.
His abilities would become more lethal. Instead of using his Rasengan to just defeat opponents, he might use it to kill. His speed and stealth would be enhanced for more effective assassinations. His ability to gather information, like he did as a ninja, would be used in a more sinister way to track down his targets.
His water - based jutsu might improve. Since Kiri is known for its water ninjutsu, Naruto could learn new techniques or modify his existing ones. For example, he could combine his Rasengan with water chakra to create a more powerful and water - enhanced attack.
His ability to move would change drastically. Vader has his slow, yet intimidating, mechanical walk. Naruto might adopt a similar gait as he becomes more like Vader. In terms of combat, Naruto's Rasengan could be combined with the dark side of the Force. It could become a more destructive and corrupting attack, maybe with a black, swirling energy around it. Also, his ability to sense others, which was based on chakra before, could now be a more Force - like sense, allowing him to detect enemies even through walls and over long distances.
In a Themiscyra fanfiction, Naruto's shadow clone jutsu could have an interesting transformation. Maybe the clones could take on some Amazonian characteristics, like their armor or weapons. His rasengan could also be modified. For instance, it could be charged with the magic energy of Themiscyra, making it not only a powerful physical attack but also having some sort of magical effect, like being able to dispel dark magic or heal minor wounds in addition to causing damage.
He might gain some of Whitebeard's physical strength. Whitebeard was incredibly strong, and Naruto could inherit a portion of that. So he could be even more powerful in hand - to - hand combat. Also, he might get some kind of seismic - sense ability, like how Whitebeard could sense things through the vibrations in the air or ground.
His combat abilities would change a great deal. He'd likely be more proficient in close - range combat due to learning the Hyuuga's Gentle Fist. This would give him an edge in battles where quick, precise strikes are needed.
In this fanfiction, Naruto's abilities would change significantly. Firstly, he'd be exposed to Kumogakure's unique jutsu. He might learn more advanced lightning - style techniques which are prevalent in the Cloud Village. His combat style would be more brute - force - oriented, as the Raikage values strength. Also, his ability to lead and make strategic decisions would be molded by the Raikage's military - minded approach. He might not rely as much on his Uzumaki heritage in the beginning, but as he grows, he could find a way to combine the Raikage's teachings with his own innate abilities.
He'd probably be better at stealth. Haku was a master of it. Naruto might also have an earlier start with water - based jutsu and could potentially develop some ice - like jutsu similar to Haku's.
His chakra abilities might be affected by the presence of Dust in RWBY's world. Maybe he could combine Dust with his jutsu. For example, using fire - type Dust to make his Fireball Jutsu even hotter. His physical abilities like speed and strength would still be an advantage, but he'd have to learn to use them in the context of fighting Grimm and other RWBY threats.
If Naruto becomes involved with Slenderman in a fanfiction, his usually cheerful and determined personality might become darker. He could be more withdrawn as he grapples with the strange and often terrifying aspects of Slenderman's world.