1. Naruto's participation in the Fourth Great Ninja War: Naruto, a member of the new generation of Konoha, only participated in the Fourth Great Ninja War as he wasn't born during the first three wars. In this war, Naruto became the main combat force and even overshadowed his teammate Sasuke. His Nine-Tails mode and powerful Rasengan made him stand out. It is uncertain whether Naruto will participate in a potential Fifth Great Ninja War in Boruto: Naruto's Next Generations.

2. Kakashi's involvement in previous wars: Kakashi, Naruto's teacher, is over ten years older than him. Despite the age difference, Kakashi showed exceptional talent during the Chunin Exams when he became a Jounin, around the same age as Naruto. He participated in the two previous Great Ninja Wars and gained fame during the Third Great Ninja War, becoming a famous copy ninja. In the Fourth Great Ninja War, he showcased his impressive skills by causing severe injuries to Kaguya Otsutsuki.

3. Onoki's long service as a Kage: Onoki is possibly the longest-living and longest-serving Kage in the series. He was the disciple of the Second Tsuchikage and participated in the Second Great Ninja War alongside his mentor. He also joined the Third Great Ninja War when he became the Third Tsuchikage. During Naruto's era, he fought alongside the other Kage against Madara Uchiha, making him an admirable character having participated in three wars.

4. The Third Raikage's unique participation in all four Great Ninja Wars: The Third Raikage, father of the Fourth Raikage, participated in all four Great Ninja Wars. He engaged in combat earlier than Onoki, participating in the First Great Ninja War. During the Third Great Ninja War, he fought thousands of shinobi alone to halt the enemy's advancement, eventually succumbing to his injuries. In the Fourth Great Ninja War, he was resurrected using Edo Tensei.

Thus, he is the only character to have taken part in all four wars.