Sasuke could be the one to stop Naruto. They have a deep bond, and Sasuke has the power to match Naruto. He might be able to reach Naruto on an emotional level and calm him down, or if necessary, fight him to a standstill until Naruto regains his senses.
In the 'naruto goes on a rampage fanfiction', it could be that Naruto is under some sort of dark magic or mind - control. This makes him lose his usual self - control and go on a rampage. He could start attacking both enemies and allies without realizing it until someone finds a way to break the spell on him.
In this fanfiction, it could be that Harry Potter has a vision of a future where Voldemort has completely taken over the wizarding world and killed all his loved ones. This drives him into a state of madness and he goes on a rampage. He travels back in time using some ancient magic he discovers, and starts to take out all the Death Eaters one by one, not caring about the consequences, as he believes it's the only way to change the future.
It could be a new dark wizard who has some personal vendetta against Harry. Maybe this wizard has a grudge because Harry defeated Voldemort and he wants to prove he's more powerful, which enrages Harry and causes him to go on a rampage.
A prevalent theme in 'naruto rampage fanfiction' is the consequences of unchecked power. When Naruto goes on a rampage, there are always consequences for himself and those around him. Also, themes of redemption and growth are common. As he comes out of his rampage, he has to face what he's done and grow from it. There's also the theme of friendship and how his friends react to his rampaging state, whether they can bring him back or not.
In a 'naruto rwby kyuubi rampage fanfiction', the plot might involve the Kyuubi's chakra influencing the Grimm in the RWBY world. The Kyuubi's rage could make the Grimm even more powerful and aggressive. The story could then focus on Ruby and her team trying to find a way to sever the connection between the Kyuubi's chakra and the Grimm. And Naruto characters like Naruto himself or Kakashi could arrive to offer their expertise on dealing with the Kyuubi.
If Naruto goes to Wakanda, he could potentially form new alliances. His friendly nature might lead him to make friends with the Wakandan warriors. He could learn about their unique fighting styles and in return, teach them some ninja techniques. It would be an interesting exchange of skills and knowledge.
In this fanfiction, Sakura from Naruto could be a main character. She has medical skills and combat abilities that could be useful in dealing with the aftermath of the Kyuubi's rampage. Alongside her, Weiss from RWBY could be a main character too. Her ice - based powers might be used to try and cool down the Kyuubi's fiery rage.
There is a fanfiction titled 'Naruto's Rampage Against the Darkness'. This one delves deep into Naruto's psyche as he goes on a rampage against the forces of darkness that have invaded the Hidden Leaf. It's not just about the action of his rampage, but also about his internal battles and how he grows through this experience. It has some really well - written character development and an engaging storyline that keeps you hooked from start to finish.