Please recommend novels about agents or mercenaries.

😋I recommend the following books to you: 1. "The Evil Emperor's Crazy Wife: The Bloodthirsty Mercenary Concubine": The protagonist was a 21st century agent. She traveled to ancient times and became a useless young lady. However, with the protection of the Nine Yin Divine Sword and the Iron Blood Mercenary Group, she shocked the world. 2. "To Marvel as a Mercenary": The protagonist transmigrated to the Marvel world to become a mercenary and fought with many Marvel heroes and villains. 3. On the Blade: The protagonist is a German intelligence professional who transmigrated to China to become a special agent, but the situation is not satisfactory. He had connections with the intelligence organization, the military, and the higher-ups of the Japanese and puppet regime. 4. "Rebirth of the Spy Battle in the Capital: The protagonist is a university student from the future. He traveled to the Anti-Japanese War and became a special agent. He fought with wits and courage in the war-torn era. I hope you like my recommendation. Muah ~