You, CEO's Secret Wife - Chapter 38

An underprivileged prodigy, a cruel, ruthless world, and an epic story of battle and conquest. A young man with an exceptional inheritance leaves the small, rural city from which he hails on a journey to find the girl of his dreams. He defeats countless prodigies, sweeps through all forces that dare to stand in his way, and progresses step by step toward the pinnacle of all the worlds!
“I’m not targeting any gods in particular. All I’m trying to say is that all gods are trash in my eyes!”

- Description from Novelupdates

To save a doomed fantasy world, I killed the main characters, then destroyed the game world, and fell into another timeline as the academy's top seat and rival to the protagonist.Now, I'm trying to save the world and steer it towards a better ending…But I'm the final boss.

Alex, a veteran soldier, meets an unexpected end on the battlefield. But instead of the final rest, he finds himself reborn into a new world—the magical realm of Harry Potter. Now a young boy, Alex is born into a Muggle family. Yet, despite his non-magical origins, his disciplined training and fierce determination uncover a rare, powerful talent for magic. With a world of spells, wands, and ancient secrets ahead of him, Alex will need every bit of his skill to face the growing darkness led by Voldemort. It’s a time before Harry Potter’s birth; James and Lily Potter are still alive. Join Alex’s journey as he navigates his way through Hogwarts, learns the mysteries of magic, and rises to face the deadly challenges that await, determined to become one of the greatest wizards in history.

I was reincarnated into another world, and I’ve brought the Horadric Cube from Diablo II with me.
Being a knight is cool and all, but being a wizard is pretty neat as well.
So, which one will it be?