Another way could be as a result of a special encounter. Maybe he discovers a hidden scroll or a mysterious artifact that imparts the power of lightning control to him. This discovery could be accidental, like when he's exploring an ancient ruin or during a battle when he stumbles upon something unexpected.
The Akatsuki members might also be antagonists. Since they're after the tailed beasts, Naruto with his additional power of lightning control would be a prime target. They might send their most powerful members like Pain or Itachi to deal with him.
Foxes are quite common. Given Naruto's connection with the Nine - Tailed Fox, it makes sense that in fanfiction, he might be able to control other foxes. They can be used for scouting or as distractions in battles.
One challenge could be controlling the intensity. Lightning is a very powerful force, and it might be difficult for Harry to rein it in. He could accidentally cause too much destruction when he just wants to create a small spark.
Maybe he discovers it during a particularly intense storm at Hogwarts. He could be in a dangerous situation, like being chased by some dark creatures, and in a moment of desperation, he unknowingly summons lightning to protect himself.
One idea could be that Naruto gains some new power or jutsu that allows him to control Anko's actions in a non - malicious way. Maybe it's a form of genjutsu that he accidentally uses on her during a training session, and then has to figure out how to reverse it.
In a fanfiction about Naruto's Lightning Release, there could be a story where a young girl discovers she has latent Lightning Release abilities. She trains hard under Kakashi to master it. Along the way, she befriends other ninjas and together they form a team. Their adventures involve using Lightning Release to solve mysteries and defeat enemies. For example, they might use Lightning Release to track down a missing-nin who has a special ability to hide from normal detection methods.
In some fanfictions, it could be an enemy-turned - ally. This character, who originally fought against Naruto, realizes his strength and potential and decides to teach him black lightning as a way to make amends or to join forces with him for a greater cause.
One implication is that his speed will increase tremendously. Lightning is known for its quickness, so Naruto would be able to move at lightning - fast speeds, making it difficult for his enemies to track or counter him. This would give him an edge in battles, especially against opponents who rely on slow - moving attacks or are not as agile.
In a 'Naruto controls snow' fanfiction, it could be that Naruto is cursed by an enemy. As a result, his chakra is somehow linked to snow. At first, he struggles to control this new power, but with the help of his friends and some intense training, he masters the ability to control snow and turns it into a powerful weapon against his foes.