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.
King Daoxiang of Zhao
Born as Zhao Yan to King Xiaocheng of Zhao, he was originally not groomed to succeed to the throne. However, his path to the throne was eased by the circumstances. Firstly, the heir to the Zhao throne was required to spend a large portion of his youth as a hostage in the Qin court - thus making him susceptible to court intrigue. Secondly, the minister Guo Kai was intent on making Zhao Yan the next king. Therefore, when King Xiaocheng died, instead of welcoming the rightful heir back to Handan, Guo Kai proclaimed Zhao Yan as king instead. The famous Zhao general Lian Po objected to this state of affairs and resigned his posts as a result.