Harry Potter: The Golden Viper - Chapter 668 - 0666 Crouch Sr.

When a fantasy kingdom needs heroes, they skip the high schoolers and summon hardened Delta Force operators.Lieutenant Cole Mercer and his team are no strangers to sacrifice. After all, what are four men compared to millions of lives saved from a nuclear disaster? But as they make their last stand against insurgents, they’re unexpectedly pulled into another world—one on the brink of a demonic incursion.Thrust into Tenria's realm of magic and steam engines, Cole discovers a power beyond anything he'd imagined: magic—a way to finally win without sacrifice, a power fantasy made real by ancient mana and perfected by modern science.But his new world might not be so different from the old one, and the stakes remain the same: there are people who depend on him more than ever; people he might not be able to save. Cole and his team are but men, facing unimaginable odds. Even so, they may yet prove history's truth: that, at their core, the greatest heroes are always just human.

“If I don’t die… I swear I will act on all my evil thoughts..”

Not exactly everyone’s typical thought when they’re about to die. What will a cowardly young man do when reincarnated with the evil powers to redefine his destiny? Can the natural kindness of human nature triumph over evil? Will he become the cold-blooded demon king of legend, or will he forge his own path and rain down another kind of terror?

- Description from novelupdates

A world from another dimension suddenly appeared in the Milky Way galaxy and collided with the earth. A spatial collapse occurred, which allowed the monsters crossing over from the other side to invade various countries, and the earth fell into great calamity.

The military was powerless against the invasion because modern weapons didn't work against monsters from another world. Under the desperate situation, a god-like figure appeared and bestowed blessings upon the humans to awaken their power. From then on, the earth regained its hope, and these extraordinary people were called Realizers.

Tenku Okuihara is a five-year-old boy who dreams of becoming a Realizer to protect the world and his family. But an incident changed his life goal from a hero to a grim reaper.

Once upon a time, a boy was referred to as a “War Hero.”

In another world called Aletia, the boy who had saved the Lost Kingdom, conquered their neighbouring countries, and led to the rise of a grand empire decided to throw everything away, returning to the modern era at the cost of his memories.

As three years passed, the boy who was happily enjoying his daily life was once again called back to the other world.

However, what awaited him was the Aletia of 1000 years in the future.

As his past glories became a “myth,” the legend of the youth referred to as the, “Twin Black Hero King,” begins.