Totalitarian Chinese regime
Pinnacle - Song dynasty (up to 80% of world GDP) around 1100 AD before being destroyed by Mongols who wiped out many cities literally.
Ming was destroyed by Manchus who also slaughtered most people of many towns in the process.
US gave China (Republic of China) the most aid during WWII (many heroic American volunteers gave their lives), and has not taken an inch of Chinese land. USSR (Russia) used China through its CCP puppet to guard its east gate against Japan, and still occupies about 1.5 million square kms of Chinese land today.
After WWII, most prominent intellectuals playing leading roles in their fields in China were educated either in the US or by schools in China founded by kind Americans (including the fathers of Chines atomic bomb, hydrogen bomb, missiles). Without the US standing up against USSR, I am not sure how many countries today would be like North Korea.
Under Mao, 1 - 2 million so called counter-revolutionaries, many of whom were WWII heroes fighting as officers of ROC, were executed.
Thirty eight million died in the Mao-made famine.
Up to 100 million were persecuted during the cultural revolution (according Marshal Ye Jianying, one of the most senior CCP officials).
I almost forgot that Mao secretly collaborated with the occupying Royal Japanese Army to fight the Nationalist army that was shouldering the major burden of fighting the Axis in the Indo-China theater (plenty of evidences from China, Japan, Russia).
One more thing, his army was growing and selling opium in large scale during WWII.
Today:
The richest 1% owns 1/3 of the country's wealth. They are doing really well, amassing wealth faster than the riches of any other countries.
More than 70% of surface water in China is polluted, so is more than 90% underground water of cities. Crop fields are often irrigated with heavily polluted water. This is why I stopped buying food sourced from Mainland China long time ago.
More than 1.2 million premature deaths EVERY YEAR due to air pollution.
Bible sales have just been banned in China. Hundreds of churches were torn down in Zhejiang province (I do not have the numbers of other 30 or so provinces).
If you want to know how the regime treats minorities, just read the stories about Uyghurs in Xinjiang (one can start with this article: http://religionandpolitics.org/2016/08/09/the-persecution-of-chinas-muslim-uyghurs). Uyghur population on their own soil dropped from 90+% before CCP taking it over to about 45% today, so they will soon become the minority on their own soil. This is happening in the 21st century and in the span of 70 years or so! When some of them managed to escape to countries like US, they feel like in heaven.
For those CCP admiring Americans, I can say with high confident, at least 80% of Mainlanders would love to swap their citizenship with you.