Tower: Rebirth of the Absolute Demon - Chapter 58: Ch : The Rise of the Tyrant

After breaking up with his girlfriend, he accidentally acquired a genius system and rose from there against the heavens, becoming invincible..

- Description from Novelupdates

In the spirit of love and in order to help his ex-boyfriends walk out from the shadow of heartbreak, every time before Ye Ming leaves after successfully completing each world’s romance mission, he will ‘kindly’ (ruthlessly) break up with with his boyfriend.

After transmigrating to N different worlds he had finally gained enough experience. At this time the system informed him that because the accumulation of his ex-boyfriend’s grievances had exceeded critical levels, leading to the failure of all his missions…. So he needs to return to each world to eliminate their grievances if he wants to complete his missions!

Ye Ming: This is an outcome I didn’t predict.

System: I tried to tell you before that if you did this you won’t have a good end.

The ex-boyfriends all laughing coldly: He He. That despicable scum that ran away after deceiving my feelings is finally back. This time don’t even think about running away!

Ye Ming: ……

System: Since you “zuo” yourself to death, even if you kneel you have to go to the end!

Ye Ming: Luckily I have a special “scum cleaning” technique ^_^

- Description from Novelupdates

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.

She thought she was dead but she woke up inside a novel – to an extra who will die a year later.Not wanting to die like this, Alexa decided to tame the male protagonist in the form of a dog. Two years from now, the male lead will return to his human form. In the meantime, she was thinking of leaving the Grand Duchy after receiving the right pay for doing them a favour.The problem is that when the male lead returns to his human form, he forgot all his memories.“You have to remember me, okay? There’s no point in looking so cute. Promise me!”She told him many times because she didn’t want to mistakenly die by the male lead’s hands, who became a villain.But,“You told me to remember, so I remembered everything. Alexa.”Ysildus unbuttoned his jacket.“If there’s no other way to return that favour then I have to pay it with my body.”A cute puppy that grew up into a weird wolf.Damn, what did I raise?