Flowers Are Bait - Chapter 24:

It has been six years since the game to decide the world’s fate began. The strongest player, Hero King Kang Yoosung, who has never lost his first place as the top ranker, greets a new season. “It was… over for me a f*cking long time ago. I’m just doing this for the money.“ [Provocation stat increasing exponentially!] [The Clown Lord expresses satisfaction with contractor’s behavior!] The survival journey of a player with insane talent begins now!

Leon a young man with the heart of a killer, did something unspeakable before getting transmigrated to another world.And what's more? He found out that due to a wish of his, he got transmigrated to the body of an incubus!And he got into the body at the worst possible time!Something happened, he managed to escape death and became the last of his race...he gained the Vice and Valor System,Lewd and immoral act could give Vice point while battle and bravery can give him Valor Point...This world has magic and beauties that none in his previous life can compare.Join the exciting journey of our MC as he gains immense strength and conquers the most gorgeous girls!

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.

Thrown into a brutal world of swords and sorcery, his memories stolen by an unseen force, Magnus wanted only one thing: to go home.But every kingdom, devil, and god — along with regressors, possessors, and fellow reincarnators — seeks to carve him apart.Survival demands war. War demands survival.And with a System that hides more than it reveals, Magnus is dragged down a bloodstained path... one battle, one betrayal, one broken world at a time.