My Hair Can Create a Demon Country - Chapter 439 - 425: Schemes!

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.

Shen Yu's world is facing the apocalypse. With the help of his Gray Mist Space, he could do good things such as saving lives to gain more gray mist and use it to do everything he wants to do. And what's more, no one but him can survive in the Space. However, this time, two figures walk out of the Space, and when they spin around, Shen Yu is shocked, because the two figures are all him from different worlds.“Your world is facing an apocalypse too?”“Indeed.”

Unconditional obedience to him? Dream on! Regrettably, after marrying Tang Yuchen, An Ruo's daily thoughts were of escape, escape, and more escape! Someone grew furious, “You want to flee? The only way out is if you die, or I perish!” Fine, she chose death! Yet he laughed wickedly, “Woman, do you intend to kill the son in your womb?”

A magical ring and a mighty spirit inside the ring, coupled with a genius who lost his cultivation and got named worthless trash. That’s Xiao Yan, the poor genius. You think Xiao Yan got it bad? Well, you clearly have not met Jing Yan.

Jing Yan was once the shining star of the whole East City. However, his cultivation dropped because of the Universal Ring that was left to him by his dead grandfather. Without anything but the Universal Ring, he will once more rise towards the top and beyond!

He is Jing Yan, The Universal Sword God.

- Description from Novelupdates