In this kind of fanfiction, Kakashi could fail to understand Naruto's unique learning style. Naruto is not a typical student, and if Kakashi doesn't adapt his teaching methods, Naruto may not progress as expected. There could also be a situation where Kakashi fails to support Naruto emotionally. Naruto has a lot of inner turmoil, and if Kakashi is too aloof or fails to notice, it could lead to Naruto making mistakes or having setbacks in his ninja journey. Additionally, Kakashi might fail to notice a hidden threat to Naruto that others around him see, putting Naruto in unnecessary danger.
One possible scenario could be Kakashi fails to train Naruto properly. Maybe he misses some crucial aspects of Naruto's development, like not focusing enough on his chakra control early on. Another could be that Kakashi fails in a mission where Naruto is involved, perhaps due to miscommunication or underestimating the enemy.
Another situation could be that Evil Kakashi withholds important ninja knowledge or techniques from Naruto. Instead of teaching Naruto valuable skills to help him progress, he keeps them to himself, leaving Naruto at a disadvantage compared to his peers. This would be a form of abuse in the context of the ninja world where knowledge is power.
In a battle situation where they are on opposite sides, perhaps due to a misunderstanding or some kind of mind - control. Kakashi, with his superior skills, could accidentally harm Naruto while trying to subdue him. For example, if Naruto is being influenced by an enemy's genjutsu and attacks Kakashi, Kakashi might have to use a more forceful defensive move that ends up hurting Naruto.
One possible scenario could be that he is captured by an enemy ninja group who wants to extract information from him. They might use various cruel methods like chakra - draining techniques or physical harm. Another could be that he is tortured as a form of revenge by someone he has defeated in the past.
In the fanfiction, Kakashi might fail because of external pressures. For example, he could be given other important missions that take up a lot of his time and energy. So, he can't dedicate enough time to Sasuke and Sakura's development. Also, he could be facing political pressure within the village that restricts his teaching methods or the resources he can use for their training. This would lead to him not being able to meet their needs and ultimately failing them.
It can change the power dynamics. If Kakashi fails Naruto, Naruto may not reach his full potential as quickly or at all. This could mean that some of the battles in the Naruto universe are lost or are much more difficult. For example, against Pain or Madara, Naruto might not be strong enough without proper guidance from Kakashi.
In some fanfictions, Kakashi might disguise himself as a sage from an unknown land. He would wear robes with strange symbols, have a long beard (maybe a fake one), and pretend to have great wisdom. By doing this, he can attract the attention of those who seek power or knowledge. He can then use this to his advantage, either to lead them astray if they are enemies or to guide the young ninjas of Konoha if they are friends.
In a more psychological approach, Naruto could have grown so much as a character that he no longer fears Kakashi's reputation. This new - found confidence could change the dynamics of their fight. He might be able to read Kakashi's moves better and anticipate his attacks. Combined with his own ever - improving skills, Naruto could defeat Kakashi in this state of mental superiority.
One scenario could be that they are in a life - or - death situation. Maybe they are surrounded by enemies and think they won't make it out alive. In that moment of desperation and realization of their unspoken feelings, they kiss. Another could be in a dream - like sequence where Kakashi has a vision of a different future with Sakura and they kiss in that vision.
Another situation is when Kakashi is on a solo mission. He might encounter a group of powerful opponents who manage to wound him. This forces him to rely on his wits and basic ninja skills to survive while waiting for backup. It can show his resourcefulness even when injured.
One common scenario could be Naruto getting into dangerous battles. Kakashi might worry about Naruto's safety as Naruto is often reckless in combat. He could be constantly thinking about how to protect Naruto or train him better to avoid getting seriously injured.