The Death Mage Who Doesn’t Want a Fourth Time - Chapter 238 - The reincarnated individuals gather before the Demon King

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.

This novel is also known as Long Live the Mad Wife!

Daughter of the Feng Family, born a waste. Forced to marry a fool in an attempt to expel evil influences. When the first killer from the 21st century possessed this body, the sky and the earth surged. She was indifferent and cold-hearted but she let her guard down around him alone. She thought he was a pleasant sheep but didn’t expect him to be a gray wolf in disguise!

- Description from Novelupdates

Nan Xun encountered a mythical beast that could take her to different worlds. She helped the mythical beast collect merit points. After collecting enough, she can go back and change the outcome of her death.

But now, now she regrets, regrets till her insides are turning green. Your mother, those merit points are collected from the scum villain with a blackening value of 100 and an evil value of 100 ah! She only wanted to purify the souls of those scummy bosses. Fu** she didn’t want them to fall in love with her ah ah ah!

Pervert number 1 eats people! Pervert number 2 is an evil ghost! Pervert number 3….

After Nan Xun realized they were all the same person, she closed her eyes and pretended to be dead.

The evil, charming, crazy Boss-sama gave her an evil smile: “Baby, weren’t you going to purify my soul? Come here.”

Nan Xun: “The evil we bring on ourselves are the hardest to bear, I really want to die, ah, what to do!”

- Description from Novelupdates

There are always four kinds of people in the traditional Mary Sue world. The Male Lead, the Mary Sue female lead, the woman who never wanted to see the female protagonist live a good life, and the infatuated man willing to destroy heaven and earth to get the female lead.