Gekitotsu no Hexennacht - Volume 2, Chapter 4: Different Sorts of People

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 more ruthless the Palace is, the more miserable the loser will end up—this he understands. But what he does not understand is, why the brother whom he lived together with peacefully in the past, would so heartlessly humiliate him today. Asking him to beg for mercy, asking him to succumb to his knees, and even… asking him to tactfully entertain him. “Yong Shan, ah, Yong Shan, as of today you are the one who qualifies to succeed as a Crown Prince, what exactly is it that you want?”

For the past 16 years, Yong Qi’s gaze was never set on him. Despite being twins with his younger brother, Yong Lin, Yong Qi has always been directing his smile and laughter towards Yong Lin, and to him, Yong Qi deliberately alienates him. He does not understand, they have the same features and looks, and he obviously is his brother too, but why won’t he be intimate with him… as if he is humiliating him. “Yong Qi, ah, Yong Qi, why won’t you understand, what I want is very simple…”

- Description from Novelupdates

“I'm a monster? Why is every player I see trying to kill me?”------------Kai, a young man paralyzed by an incurable disease, decides to play the new VRMMORPG called Realms of Monsters in search of freedom and adventure. However, when he logs in for the first time, something unexpected happens.While everyone else chooses their class and race, Kai awakens in the middle of a forest... as a salamander.Luckily for him, he won't stay a salamander for long.[Mythical Evolution System activated.][Devour a monster to evolve.]Trapped in a monstrous form, Kai must navigate a hostile world where every player is a potential enemy. With the Mythical Evolution System, his survival hinges on his ability to evolve and grow stronger. In a game where everyone else is a hunter, can Kai rise from being the hunted to becoming the ultimate predator?

Jun Xie was the number one assassin in modern earth. His skills and knowledge in the field of assassination were unparalleled, his accomplishments unprecedented, his reputation terrified the entire underworld. However, during a mission to retrieve a mystical treasure, a mishap occurred…

He is now Jun Moxie, a sixteen year old super level debauchee, sole heir to the declining Jun family. A family of valiant heroes, left with an old grandpa, a crippled uncle and a debauchee as the sole heir! Accepting the world’s criticism and cold stares with a smile, his new journey begins! His life will be carved by his own will! Rise to the top! Evil Monarch Jun Xie!

“This cup I toast to those I’ve killed in my past life. Forgive me, for there is no chance for you to have revenge. Gulp!

This cup I toast to those whose life I will take in my new life. Forgive me, for you are fated to die by my hands. Cheers!”