A Reincarnated Mage's Tower Dungeon Management - Volume 1, Chapter 2 – Demon Lord, Premonition of Liberation

Jiang Li traveled through time and found himself without any cheat tools, so he could only rely on diligent cultivation. After five hundred years, he became the strongest person in the Nine Provinces.Suddenly, a system appeared, claiming to be able to help him go from being a Qi Refining cultivator to becoming the number one person in the Nine Provinces.Jiang Li looked at the first task and fell into deep thought.“Please defeat your cousin, who is at the sixth level of Qi Refining.”“Your system has quite a delay,” he said.

Witnessing her boyfriend cheating on her with her bestie, Shiyao was so angry that she went to a pub for fun and met a man, who was really a piece of work. After a crazy night she fled away, but was embarrassed to know that the man she slept with was her boss You Ze.
Jesus, give her a break!

- Description from Novelupdates

I became a side-character who died in anguish because of her good-for-nothing husband.

If I can’t avoid getting married, why don’t I change who I marry instead?

“Excellent, marriage sounds good.”

“Wise choice. Then let’s have a wedding ceremony that isn’t too ceremonious. Following that, I’ll need you to go down to the Fief and behave like the lady of the house until I call for you. Naturally, there won’t be any time to spend in leisure whilst dousing yourself in luxuries.”

“I’m not marrying you, but your father instead.”

“……Pardon?”

“I’m not going to marry you. Do you have a problem with that?”

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.