The Grand Secretary’s Pampered Wife - Chapter 706.2: The Truth of the Past

After transmigrating, Chen Yu found himself in a highly militarized world. But the “will of the world” had concluded that he was an intruder and put a curse on him.

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

He died on the wedding of the girl he had a crush on, after a long and successful career. After convincing Yama to send him back to the world, he decides to fix the areas in which his life went wrong. Realizing the lack of love and romance in his past life, he sets out to conquer the hearts of various women.

- Description from Novelupdates

The dark BOSS, who had the privilege of being the last living person on the planet, and the second-oldest brother on the planet was born again.

What should he do after he was born again? Was it to rule or destroy the world?

BOSS said that he was not interested in these, he just wanted to die. In order to let the boss who was bent on ending his own life live, he was omnipotent, and he will be comfortable with the boss, and then helplessly find out…

BOSS was more and more wrong with the style of painting!

- Description from Novelupdates