One possible antagonist could be Orochimaru. He has always been interested in Naruto for his Nine - Tails power, so it would make sense for him to be a threat that Kakashi has to protect Naruto from.
The appeal lies in the dynamic between Kakashi and Sakura. Kakashi is a highly skilled and respected ninja, and seeing him come to Sakura's rescue plays into the idea of the strong protecting the vulnerable. It also shows their relationship, which can be explored in different ways in fanfiction.
In some fanfictions, Sakura is captured by an enemy who wants to use her medical knowledge for evil purposes. Kakashi tracks her down, using his tracking skills and his knowledge of the enemy's motives. Once he finds her, he has to fight off multiple guards. He uses his strategic mind to outwit them and finally saves Sakura. This kind of story often shows the strong bond between Kakashi and Sakura in the Naruto universe.
One common theme is friendship. Sakura's act of saving Kakashi shows the strong bond between them as comrades. It emphasizes how much she values him in the Naruto universe.
The moment when Kakashi actually reaches Naruto and stops him from harming himself is crucial. He could use his speed and strength to grab Naruto's hands if he was about to use a weapon on himself. Kakashi's presence alone at that moment can be a shock to Naruto, making him pause and re - consider.
Well, it could be that in the fanfic, Kakashi saves Naruto from a trap set by Orochimaru. Kakashi arrives just in time, using his lightning - style jutsu to break through Orochimaru's defenses and snatch Naruto away from the clutches of danger. This would create a tense and exciting moment in the story.
You can try looking on fanfiction websites like FanFiction.net or Archive of Our Own. Just type in 'Sakura Saves Kakashi' in their search bars and you should get relevant results.
One possible antagonist could be the Akatsuki members. They are always looking for strong opponents or valuable information. Maybe they target Iruka because they think he has some knowledge about Naruto that they can use, and Kakashi has to stop them.
In such a fanfiction, perhaps Kakashi might save Iruka from a dangerous enemy like Orochimaru's minions. Kakashi, with his Sharingan and powerful jutsu, could arrive just in time to fend off the attackers.
In some fanfictions, Naruto saves Kakashi from the brink of death. For instance, Kakashi could be poisoned by a rare and deadly toxin. Naruto, with his determination, goes on a quest to find the antidote. He overcomes many obstacles, battles different creatures, and finally retrieves the antidote to save Kakashi. This showcases Naruto's loyalty and his growth as a shinobi.