I'm only one year old, what the heck is a Overturning System?! - Chapter 39 - 34: The Path of the Grand Void, Li Qingzhou

At 18, Alex Kain is whisked away to Eryndor, a game-like realm where he gains 'Skill Synthesis', a talent to fuse skills into godlike powers. Battling monsters and conquering dungeons, he builds a harem of strong women drawn to his might and charm. With the power to return to Earth bearing incredible resources, Alex faces a growing threat that endangers both worlds in this epic of adventure, romance, and ambition.

Overnight, Tangning became a big slave owner in the southern United States with three large plantations and hundreds of black slaves who could be driven at will.

Tangning was very satisfied with the result of such a time-travel, but then he sadly discovered that he could only enjoy three years of such a good life, because three years later would be the “Civil War”, what should he do after this?

- Description from novelbuddy

A failed investor from 2017 got drunk and woke up in the 1980s. China is just opening up, and the economy is blooming. There is also the dissolution of the Soviet Union, the bursting of the Dot-com bubble and other financial crisis. He used his knowledge of the future and slowly build up his empire.