Bai Qi.
Bai Qi, also known as Gongsun Qi, was a general of the Qin State and the leader of the "Four Famous Generals of the Warring States Period" (Bai Qi, Lian Po, Wang Jian, and Li Mu). Bai Qi was good at using troops. Historical records record that he "anticipated the enemy's combined changes, made endless surprises, and shocked the world." He fought for 37 years in his life without a single defeat. He defeated the six kingdoms so that no one dared to take command to face the enemy, and made an immortal contribution to the unification of Qin. However, he killed 400,000 surrendered soldiers of Zhao in the Battle of Changping. , but was forever relegated to the "cold palace" by orthodox historians and was not allowed to be among the famous generals.
Extended information:
Bai Qi's archives were blank before 294 BC, and there is no record of him in history books. In 294 BC, outside Xincheng in South Korea (today's southwest of Yichuan, Henan), Bai Qi showed his sword for the first time and commanded the battle of Xincheng as Zuo Shuchang (equivalent to a mid-level general). He won the first battle and initially demonstrated his military talent. At this time, 62 years had just passed since the era of reform initiated by Shang Yang. In the next 37 years, Qin entered Bai Qi's era of conquest.
The Battle of Changping ended with Bai Qi's victory. Zhao Kuo was desperate and was shot to death by the Qin army. 400,000 soldiers surrendered. However, Bai Qi made an incredible decision - in order to prevent the surrender of troops from rioting, in addition to sending 240 young Zhao soldiers back to report the news, all 400,000 people were killed! The State of Zhao was shocked, and the Seven Kingdoms were shocked. This has also become a strong mark left by Bai Qi in the history books. Even though he has a lifetime of undefeated military exploits, the fact that he trapped 400,000 soldiers has become a crime that Bai Qi will never be able to defend.
Reference material: People's Daily Online - Qin's famous general Bai Qi: "God of Killing" or "God of War"