Wu Sangui

Wu Sangui was a Chinese military general and warlord during the late Ming and early Qing dynasties, infamous for his pivotal role in the fall of the Ming Dynasty. After initially serving the Ming, he famously opened the Shanghai Pass to allow Qing forces to enter China as a means of revenge against the rebels who had captured Beijing. However, this decision ultimately led to the collapse of the Ming regime and the establishment of Qing rule, demonstrating the peril of relying on external powers for personal grievances.