Otherworld Advance Team - Chapter 73 - 69 Encounter with Kali Again

Eren Idril died as an old, decrepit, and piss-poor adventurer by the maws of a D-Rank monster. He had a lot of unfulfilled dreams and desires that couldn't see the light of the day after the light in his own eyes died down.

But fortunately for him and unfortunately for the world, that wasn't his end. Eren was somehow dived back in time when he was a mere teen, attending Lionheart Academy for adventurers.

When life gives him a second chance, Eren decides to exploit it to its fullest. Experience his vile deeds as he partakes in them without feeling the slightest bit of hesitation.

A decade ago, the first dungeon gates appeared, but some vanished before they were ever conquered. The MC, a low-rank hunter, awakens the Lost Gate System, granting him access to these forgotten dungeons where legendary monsters and artifacts are trapped. Each completed lost gate grants him absurd power, but also reveals terrifying truths—these dungeons are prisons for ancient beings who want revenge.

He is an extremely wealthy empire president who is obsessed with his wife and loves to pamper her.

One day, the bodyguard came to report: “Master, the young lady has gone after her fiancé!”

“Master, the young lady confessed her love live worldwide!”

“Switch the photo and name to mine!”

“Master, madam, go to the hospital to have the child aborted!”

The handsome and noble man was furious, “Get the young lady back to me so that I can serve her well! Stop, I will catch you myself!” [After Marriage]

Su Fu glared at her extremely possessive husband: “Get a divorce, we can’t survive this life!” Shangguan Ling smiled coldly: “It’s just that, whoever you don’t leave is your grandson! I will give you the property and the little buns, and I will give you the property.” Here you go! Wherever you go I will go too!” (Nuan Chong)

- Description from novelbuddy

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.