Side Character Transmigrations: The Final Boss is No Joke - Chapter 142

When an S-class elite assassin-raised captain of a special ops suicide squad comes home from a high-stakes Africa mission, he finds himself offered something that could potentially set him up for life- a curious assignment that he could use to finally exit his days of war and slaughter.

Then placed into a high-school setting, Lin Yi is tasked by the chairman of a top-tier multi-billion company with bodyguard duty for non-other than his own daughter, a certain little Miss of said high-school.

His enemies, once ranging from drug lords, mafia bosses, political figures, and national leaders, are soon replaced with spoiled kids who happen to have rich papas and mamas, and Lin Yi finds his intense expertise and high-threat skillset misused, and very underwhelmed…

But he does get a harem cast as diverse as his old enemies, so Lin Yi decides that, for the sake of messing around with girls as an invincible entity in a down-leveled environment, leaving his bloody and death-filled war days behind is something he’d definitely want to strive for.

- Description from Novelupdates

She, Xue Fanxin, a famous medical genius in the 21st century, had transmigrated into the body of the dumb daughter of the Grand Duke.

Betrayed by his former gang and thrown into the Rendhold Underprison, Dantes has spent the last five years scraping by. A whoreson of orcish, human, and elvish blood, he's lived on the periphery of the periphery, lying, cheating, and stealing to survive. After a run of bad luck, he's made a powerful enemy. Luckily, he's also gotten all the tools he needs to turn things around.A slow burn progression fantasy focused on rising through the criminal underworld of a city-state using newfound powers and quick wits.MC's powers will develop slowly, but he will use them in creative ways to get ahead, and in the meantime he's not above just braining someone with a club.Anti-hero/villainous MC with a code.

The long night shrouds the world, and the dawn is late in coming.Evil descends upon the land, causing immense suffering to all creatures.He roams through the long night, wanders on the edge of the blade, and sways between the clouds and hell.Igniting the fire of the star soul.Since the night is long, then I shall be the lord of the night.