The Retired Hero is an Extra - Chapter 225 Undesired

The scum’s or villain’s long road of transformation was tentatively set to the world:
The abandonment of the educated youth’s wife (Completed)
The hidden marriage of the scum film emperor (Completed)
The best brother in the world (Completed)
The Phoenix male who destroy the bridge after crossing the river (Completed)
The treasonous general (Completed)
I’m an honest man (Completed)
To become the top scorer in the School of Agriculture (Completed)
The soft rice man’s self-cultivation (Completed)
The whole world is reborn (Completed)
I want to survive on a desert island (Completed)
The stallion male who has seized the opportunity (Completed)
The perverted self-salvation (Completed)
The spring of the loafer (Completed)
The misplaced life (Completed)
The miser career (Completed)
The ghost is out of feeling (Completed)
The Queen’s favorite husband (Completed)
The vicious girl with her godfather (Completed)
I want to be a good person (Completed)
I does not tear up the family (Completed)
The perverted common plant (Completed)
The Mary Sue’s men (Completed)
Every time I was reborn, someone wants to kill me (Completed)
The old people’s counterattack path (Completed)
The global evolution (Completed)
When I became a net red (Completed)
For you, good person (Completed)
His heart had white moonlight (Completed)

- Description from Novelupdates

This story is set during the end of the Sui Dynasty, a time where multiple powers struggled for supremacy and power.

Into the fray enters two orphans Kou Zhong and Xu Ziling; these two youths by many chances and luck obtain ‘The Secret to Long Life’ allowing the two to obtain profound martial abilities and a chance to rise to the top in this age of turmoil.

In fact, Ling Yun was the son of a wealthy businessman. But one day, his mother finds out that her husband is having an affair with his secretary. And after that she decided to divorce her husband, but at that time she did not realize that she was pregnant with Ling Yun.

After learning about her pregnancy, she decided to move to another city. And since then, their lives have been up and down. Because of the economic crush, and also his mother's health was getting worse.

He decided to take the 'Dark' path, which led him to near death. But just as Ling Yun was nearing his end, he heard a little girl's voice asking him.

“Do you want to live?”

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.