Harry Potter: Eclipse. - Chapter 34:

What should I do if I cross to another world and become an NPC?

This idea has been deeply rooted and sprouted in William’s mind!

Therefore, he decided:

I want to be the strongest NPC in history.

Wear the thickest armour and give the most vicious beatings!

Who says an NPC will be killed by players?

Who says an NPC upgrades more slowly than players?

Who says an NPC must explode equipment, I can explode in more ways… Bah humph.

Anyway, it’s impossible for me to die. Just take a look at all you trash players. Your father will stand here and let you chop for an hour without a frown!

- Description from Novelupdates

In the beginning, I just wanted to solve life problems.

Then, I didn’t want to admit defeat, I didn’t want to just leave in such a daze.

Next, now that you’ve stood your ground, why not do it better.

Finally, as I have always insisted, when you decide to invest in something, you must do it to the best of your ability!

– One of the greatest actors of the 21st century, Sean Tang

- Description from novelbuddy

The Honoured One... A title bestowed upon the one who's pleasure and displeasure matter above all else within the bounds of Heaven and Earth.That is who I have become. Satoru Gojo - The Six Eyes may have claimed this title for himself, declared it to all of Creation and went unchallenged for it for years, till the awakening of the man I have been transmigrated as.I intend to honour that title.Power is meant to be used - to change one's life with.And change it I shall.----------------------------(Author note: This guy will be a lot like Sukuna in personality, but not a carbon copy - he will have his own views and thoughts that will contradict canon Sukuna, cause this guy is a transmigrated soul from our world who was thrown into the Invincible world with all of Sukuna's powers.Also, he was geniunely Sukuna in his past life.Romance: Sukuna X Yandere EveSukuna is in the body of Megumi (Shadows yet to be tamed)Read the auxiliary chapter for Sukuna's power level compared to this world, because I am taking some vague statements about Sukuna in JJK canon, to make him strong enough to not just be crushed in an instant in a world with Viltrumites.Hope to see you guys soon,Bye!)

Zhang Xuan traverses into a foreign world and becomes an honorable teacher. A mysterious library appears in his mind. As long as it is something he has seen, regardless of whether it is a human or an object, a book on its weakness would be automatically compiled. Thus, he became formidable.

“Emperor Haotian, why don’t you like to wear underwear? To think that you’re still an emperor, can you pay more attention to your image?”

“Fairy Linglong, if you continue to suffer from insomnia, you can always look for me. I have a way with lullabies!”

“You as well, Qiankun Demon Lord, can you cut down on the garlic? Do you want to stink me to death?”

…

This is an incredible story about the heritage between teacher and students, cultivating and guiding the world’s strongest experts.