Final answer:
Nikolai Rimsky-Korsakov was the leader and mentor of the Russian Mighty Five, combining Russian and German styles. He was a renowned composer and music teacher, known for his influential contributions to Russian music.
Step-by-step explanation:
The leader and mentor of the Russian Mighty Five, who combined Russian and German styles, was Nikolai Rimsky-Korsakov. He was a renowned Russian composer and music teacher, known for his compositions influenced by both Russian and German musical traditions. Rimsky-Korsakov trained from an early age as a pianist and went on to become a prominent figure in the Russian music scene, mentoring and inspiring other composers of the Mighty Five.