I Am Overlord - Chapter 1833

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.

The age of darkness has arrived.

The price for saving the world is the right to rule it. After saving a faraway land, Lyn Rivers was cast back to Earth. Wanting the admiration, prestige, and glory of saving that realm, she forced her way back. But she was forgotten, and someone else claimed credit for her deeds. Now, with the power of a deity of destruction, she desires nothing more than to claim her place in history. To do that she will conquer dungeons, make alliances, destroy kingdoms, and build an empire. After all, why ruin the world when you can bend it to your will?

The frail and sickly Wen Jiexi had always wanted one thing: a healthy body and like a dream come true, one day, she was selected by the system!

System: The amazing me shall grant you a strong physique and divine strength! However, you have to maintain your health through monthly missions! If you fail to complete them~well, then you’ll stay as a female King Kong, forever~

Wen Jiexi: What?! Will I no longer be able to live my life freely again?!!

Mother with an alarmed expression: My frail daughter is actually trying to do the most sit-ups possible?!

Father made a strange face: My delicate daughter ran on the treadmill for an hour?!

Brother’s expression crumbled: Can anyone tell him how his cute little sister who is as precious as a delicate white flower…was actually able to use one punch to break a sandbag and smash a hole through the wall!!!

Through a series of unexpected circumstances, she was pulled into the entertainment industry and became a female martial artist!

Female Fan: Our darling Wen is the most awesome! She’s even more handsome than a man!

Male Fan: The girls today are so domineering! To be able to throw away all of one’s shame, I want that feeling too!

The frozen expression after being hugged by the princess from behind: …..

Wen Jiexi held up a hand: No, no, no! It’s not like that!

- Description from Novelupdates