Cloud has his iconic Buster Sword skills. In a Highschool DxD fanfiction, these could be translated into a very powerful physical attack ability, perhaps even on par with some of the high - level sacred gears. His speed and agility in combat would also be a great addition, allowing him to quickly move around the battlefield.
As a teacher, Cloud might struggle with the more magical aspects of the DxD curriculum. But he could offer his own unique perspective on combat strategy. He could train students to be more adaptable in battle, using his own experiences of facing different types of enemies. His no - nonsense attitude would likely clash with some of the more carefree students, but he would also earn the respect of those who are serious about improving their skills.
He would bring his chakra powers for sure. His ability to use jutsus like Rasengan would be a powerful addition. Also, his enhanced physical abilities due to being a demigod, like super strength and speed, would make him a formidable opponent in the DxD battles.
Cloud Strife would likely be a bit of an outcast at first in the Angel Highschool DxD setting. His serious and brooding nature might not fit in with the more flamboyant characters. However, his sense of justice could lead him to get involved in the battles against the various evils in the DxD world. He might form an unlikely alliance with some of the devils or angels there, gradually learning about their world and how to use his skills to help them.
Devil Naruto might possess the power of flight, which is common among devils in Highschool DxD. His chakra could be infused with devil energy, making his jutsus more powerful and having additional effects like draining the opponent's energy. His shadow clones could also be enhanced to have some devil - like characteristics, such as being able to resist certain types of attacks better.
He could still have his chakra - based powers. His Rasengan, for example, would be a powerful attack. And with his heightened senses, he might be able to detect and counter attacks more quickly. He could also develop new techniques that rely on his other senses, like a sound - based jutsu that can stun opponents.
Cloud could fit in by being a transfer student with a reputation for being a lone wolf. In the Highschool DxD setting, he might initially seem out of place. But his skills with a sword could be seen as a form of sacred gear - like ability. He might not be interested in the usual high - school drama, but get dragged into it because of his sense of justice, which is a big part of his character.
He would definitely still have his chakra powers. His ability to create shadow clones would be a great asset. Also, his sage mode, if he could access it, would give him enhanced strength, speed, and sensory abilities in the DxD world.
He could have the power of the Ouroboros, which might give him the ability to manipulate energy in ways unique to the Highschool DxD world. Maybe he can create powerful energy shields or attacks.
He would probably have Naruto's regular ninja powers like the rasengan and shadow clones. But combined with his Azazel heritage, he might also have some unique fallen - angel - like abilities. Maybe he could fly or have some sort of dark energy - based attack.
A plot could involve a merging of the two worlds. Due to some mysterious magic or scientific experiment gone wrong, the Naruto and Final Fantasy VII worlds start to blend. Naruto and Cloud Strife are two of the few who are aware of what's going on. They have to work together to find a way to separate the worlds again. Along the journey, they encounter various characters from both universes. Naruto might meet Aerith and be fascinated by her healing abilities, while Cloud Strife could meet Kakashi and learn about his Sharingan. They face many challenges, including battles with enemies who have also been affected by the world - merging, and in the process, they develop a deep respect for each other.