Dungeon King: A Lady Knight Offered by My Goblins - Chapter 571 Slaying

On earth, Felix is just a normal guy, a bit of a loner but otherwise normal. In the multiverse, under the rule of The System, he's a caster. Fascinated by magic and hungry to learn, grow and discover, this series follows Felix on his adventures through the integration and beyond.

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.

In a world where villains are crafted, not born, Vyan's life takes a detour from dull to downright dramatic faster than he can say “abracadabra.”Meet Vyan, the most ordinary knight in the realm, with all the magical prowess of a damp sock. Loyalty? He's got it in spades. Betrayal? Well, that's the surprise twist in his not-so-fairy-tale life.Framed and forsaken, Vyan is left with nothing but a grudge and some pretty gnarly scars, courtesy of his once-master, Iyana. Oh, did he mention she is the daughter of a marquess and the object of his unrequited affection? Talk about adding insult to injury.Just when he is ready to unleash his inner berserker, a butler comes along with news that makes his hair stand on end: Vyan is the last heir of the Grand Duke's mage dynasty!With power crackling at his fingertips and more mana than he can shake a wand at, Vyan is ready to show the world what happens when you underestimate the underdog. Will Vyan rise from the ashes like a phoenix, or will he crash and burn like a fire-breathing chicken? There's only one way to find out.

Criminal Psychologist, Su Xiao Pei, who was an leftover woman in her modern life, was informed by the God Of Marriage, Yue Lao, that her destined lover was in a car accident, his soul was sent to another world. Su Xiao Pei was ordered to bring back this strange man who was connected to her by the red string of fate. Otherwise, she will live the rest of her life in loneliness, with no one to support her.
But how does that man look? No idea.
What’s his personality like? No idea.
What does he do for a living? No idea.
Can she not go? Of course not.
Su Xiaopei, who believes in all things logical has run up against a serious wall this time.
The bottom line: This is a story about a modern female psychologist who has traveled back in time and an adorable warrior as they talk about love and solve crimes.

- Description from Novelupdates