One Piece: I'm Destined to Be the Son-in-Law King! - Chapter 257: Sweeping Away the Generals

A man is reborn into the world of Avatar: The Last Air Bender as a waterbender from Katara's tribe. Best of all, he was the same age as her, and he had a system with him to help.He knows the future and a system that lets him continuously get stronger by completing quests or long-term missions, as well as giving him the ability to copy abilities from others for himself. He will become invincible in the world of Avatar, even more so than the Avatar himself.

I lived for you in the last lifetime, everything I did was for you, yet you wanted me to die; so, this time, life is mine to live! This world lied to me, betrayed me, and humiliated me, and I am back to change everything!

- Description from Novelupdates

A little ruffian who fought recklessly without any morals and bottomline accidentally time-traveled to parallel space and became a Key Case Investigation Team agent. The huge change in identity had him creating chaos in the police station. However, a strange miracle system helped him repeatedly solve mysterious cases, turning him into an impudent ruffian detective!

Through an array of coincidences, Alex comes to learn that making pills is one of the best ways to earn money in the game, 'Eternal Cultivation.'