Qin Shihuang should be familiar to everyone. Although he was a tyrant, he still made many contributions during his service. For example, when Qin Shihuang was in power, he unified the units of measurement, and he also unified the writing. The Great Wall of Wan Li was also built at that time, which resisted the attack of Xiongnu at that time. Until now, the Great Wall of Wan Li has been a key tool to resist foreign invasion. Moreover, some policies during his reign had an impact on the dynasties at that time, and some even remained.
The second is Liu Heng, the emperor of China literature, who was also peaceful during his reign. When Liu Heng was in power, those water conservancy projects were built, and some criminal laws were abolished, which reduced the tax revenue at that time. People like him better, and he gained great popularity. Not only that, he is also very frugal, and his own things are not too extravagant. Moreover, he also stipulated that those counties and countries should not be too extravagant. He is a good emperor.
The third is Li Shimin, Emperor Taizong. We all know that he established the prosperous age of the Tang Dynasty and realized the rule of Zhenguan. During the reign of Emperor Taizong of Li Shimin, there were many exploits, because the territory at that time expanded a lot, and the people at that time lived a very happy life. Li Shimin still has a way of governing the country. He is very open-minded and will accept other people's opinions. Besides, he is also very frugal.
The fourth is Emperor Kangxi of the Qing Dynasty. Emperor Kangxi ascended the throne at a young age, but he was young and promising. When Emperor Kangxi was in power, there were also many achievements. He conquered many places, put down the rebellion, and recovered Taiwan Province Province, which improved the territory of China to some extent. Moreover, during his reign, he was diligent every day, which also created the prosperity of the Qing Dynasty. Therefore, some people in past dynasties called Emperor Kangxi the emperor.
These four emperors are all famous in our history and have made great achievements, so I think they can be called the greatest emperors.