Devil Gambit - Chapter 34 : Judgment Day in Sweatpants

In his past incarnation, Lu Xuan was the youngest Celestial Lord that the universe has ever seen!
An accidental rebirth brought him back to a thousand years before, where the Earth had just begun its spiritual reawakening. When he stepped onto the way of cultivation for a second time, he swore to rewrite all injustices suffered in his past life, and defeat all enemies that dare stand in his way!
Let invincibility be his cultivation and the path he treads. In this life, it is his destiny to be invincible!

[You have been chosen as a Lord of the Intergalactic Lord Project.] [Your reward: A floating island to call your own.] [Your mission: Build your kingdom, summon legendary allies, and dominate the worlds!] [Your advantage: An SSS-grade Ultimate Gacha System.] Atlas Blackthorn, the newly chosen Lord of a floating island, wields the power to summon legendary warriors, powerful artifacts, and, of course, waifus. With boundless ambition and the Ultimate Gacha System at his side, Atlas sets out to become the strongest Lord in all worlds. How far will his ambition take him?

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.