In the MCU/Marvel with the Omnitrix/Ultimatrix - Chapter 27: I want big green to be my friend

What happens when a fanfic author with a habit of lying and scheming suddenly finds himself as a self insert during Duelist Kingdom? What happens when you have Yugi, Joey, Kaiba, and the rest encounter someone who knows all about every major player in their saga... and sees no problem with abusing said knowledge? Chaos, dear reader. Sweet, sweet chaos

“Legend had it that in the deepest part of the oldest galaxy, there was a door as red as blood and fire.

Legends and myths, darkness and light, countless stories passed through this old door.

The Door of Constellation that overlooked everything would warn the sky and earth, sending darkness back to where it belonged.”

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

11-year-old Jung Si-woo always had to play alone during PE class.

“I’m excluded from any ball games.”

“Are you kidding me? Why are you the only exception?”

“If I play with the rest, everyone will be excluded. Physically.”

The strength that Jung Si-woo has is not from any hard training but just a power he was born with.

When he turns 16 years old, the world faced a cataclysm, a huge castle appeared over the Earth out of nowhere. It began selecting special humans to grant them wings making them a Player and that soon changed the world.

10 years passed.

Jung Si-woo with a supernatural strength has still not been able to forsake his dream to be a Player. While he was enjoying his jobless life, he saved a falling Player and unknowingly met the requirement to be a ‘Underground Player’.

He became more special than anyone ever is! Now, Jung Si-woo brilliant dungeon strategy play begins.