King Zhaoxiang of Qin
Reigning over 55 years, he was one of the longest-serving rulers during the Eastern Zhou Dynasty. Although making numerous policy mistakes during his later years, his aggressive territorial expansions were pivotal in consolidating the state of Qin as the dominant military powerhouse in the late Warring States period. It was the strategic dominance established during his reign that paved the way to Qin's eventual successful unification of China under his great-grandson, Ying Zheng.
Ziying
Ziying (died January 206  BC) was the third and last ruler of the Qin dynasty. He ruled over a fragmented Qin Empire for 46 days from mid-October to early December in 207  BC. He is referred to in some sources with the posthumous name Emperor Shang of Qin (秦殤帝), despite Qin abolishing the practice of posthumous names. (In Chinese tradition, even someone who never held a ruling title while alive might be given the posthumous title "emperor" after his death.)