Re:Zero Kara Hajimeru Isekai Seikatsu - Chapter 68Arc 7, - “Guidance of the Sword Wolf”

After being reborn in a sci-fi ABO world, Xi Wei became the newly born son of the Imperial King. He thought, as the emperor’s son he could live a carefree and imposing life, but unexpectedly the First Prince is actually an omega? What the hell is an Omega?

With the Legendary Mechanic System, I transmigrated to Marvel Universe to be Dr. Zola’s assistant.

With Mechanical Force Analysis, I can learn every black technology.

Winter Soldier’s arm? I built a better one for you.

Iron Man’s armor? I already made it a decade earlier.

Doc Ock’s tentacles? I am the one who provided core technology.

Hulk’s mutation? Sorry, I was there and got hit by the radiation too.

As for a certain purple potato, can he collect all Infinity Stones?

……

However, I only had one simple ultimate dream. That is to go home…

- Description from Novelupdates

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