Who were the four most upright officials in ancient times?

Roughly so

Han Dynasty: Liu Chong, Yang Zhen, Su Zhang, Zhao Guanghan, Huang Ba

Southern and Northern Dynasties: Su Qiong, Gu Xie, Chen Konghuan , Yao Cha, Yuan Yuxiu, Pei Xia

Tang Dynasty: Xu Yougong, Di Renjie

Song Dynasty: Bao Gong, Chen Xiliang, Liu Wensou

Ming Dynasty: Kuang Zhong , Hai Rui, Zhou Xin, Wang Pu

Qing Dynasty: Yu Chenglong, Lu Huang, Tang Bin, Zhang Boxing