My Wife Is A General Who Killed Tens Of Thousands On The Battlefield - Chapter 293 - Increasing One’s Strength

A good-for-nothing man married a beautiful girl but was kicked off the bed on the wedding night. Furiously, he wrote a bill of divorce and ran away.
He was schemed a car accident in which he nearly lost his life. However, it turned out to be a blessing. He swallowed the soul that passed through the outer world, thus obtained superb medical skills and martial arts.
Later on, with the silver needles and invincible martial arts, he embarked on the road of counterattacks and was committed to his great dreams.

- Description from Novelupdates

One rule: Survive. Everything else is optional.Reika Kagetsu doesn’t want to be a hero. She just wants to feel—pain, fear, adrenaline—anything to remind her she’s still alive.Tenshiko Academy promised her that.What she got instead? Brutal training. No rest. No second chances. And monsters—inside and out.Now she’s fighting the Shikiban: creatures born from blood, madness, and buried secrets. But the deeper she goes, the more she begins to wonder...What if she’s one of them?Power always comes with a price. And Reika is about to pay it in full.

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.