Ultragene Warlord - Chapter 13: Scorpion Horde

There was nothing left to lose in his life.He had lived as a hero. He had started at the bottom and worked his way up to the top, at the end he become the best, yet he had always been betrayed by those he had tried to protect.Humanity did not deserve his protection.When everything went out and he could no longer even hope to beg for his life, he could do nothing but look up at the blood-red sky among the corpses of demons and angels.He wished for one more chance, just one more chance.And when that chance was given to him, he swore that he would change everything. He would no longer be a hero to save people, but an anti-hero to save the world.Sacrificing hundreds of people to save an elf, poisoning hundreds of people to save a group of half-demons.He didn't care about any of that anymore, he would protect those he cared about and send everything else to hell.Not even the gods or goddesses could stop him.

When she reborn, she finally understood; men can never be relied on.
That being the case, she can only rely on herself to win, that
splendid brilliance she yearned for, in this lifetime.

To my scheming Stepmother and ruthless sister, I will
destroy all your backings, pull off your wings, and step on your
arrogance! As for Grandmother whom speaks kindly but has a snake-like heart,
and a father who is hypocritical and exploits advantages; I will tear
off your pretense and cut off your hope! Let’s see how you can still
scheme against me!

Witness her splendid fight against her stepmother, punish scum men,
and create havoc in the imperial court, as she soars with the wind and
rises above the water!

But as for that man who still stands! How dare he play with my heart?

- Description from Novelupdates

The tens of thousands of universes have merged. The disintegration of spiritual force led to the momentous collapse of the great Cultivation World, a mighty era that had endured through millions of years of history. In the wake of the large-scale invasion of the Wilderness, the Avalon of Five Elements has become the practitioners’ last stand.

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.