Counterattack System appeared when I'm already At The Mahayana Realm - Chapter 756 - 755: Both of you can go on together.

An Individual from Earth finds themselves in the Shinobi World, equipped with a Scientific System. From that moment, he delved into scientific research far ahead of its time.

Lingyun, a fierce and savage cultivation genius takes over a dead teenager’s body. Coincidentally, they are both named Lingyun. Set in a alternate version of the 21st century, teenager Lingyun has been killed by someone with a grudge.

- Description from Novelupdates

The nuclear holocaust which caused the collapse of the Old Times on Earth should have wiped out all human life on the planet. Yes, the gods set up their beautiful Elysiums to provide sanctuaries for their chosen, but by all rights everyone outside the elysian lands should’ve perished long ago. Yet somehow, human life still managed to persist, even in the deadly, mutant-infested wastelands.

Cloudhawk was a young scavenger who dreamed of being as free as the hawks in the skies, yet seemed destined to live out his life scrounging for scraps in the wasteland ruins. Fate, however, is ever-fickle. A chance meeting with a ragtag group of mercenaries changed the trajectory of his life, bringing him into a world with mutants and metahumans, demonhunters and godslayers, and even gods and demons. Cloudhawk would find his own place in a world that was far greater than he had imagined, find his own path between the zealous light of Sumeru and the whispering darkness of the Abyss… and one day, he would find that even gods may fall.

Li Xuehao found a secret of monasticism in the cover of the genealogy. After spending ten years, he finally succeeded in building the foundation. Unexpectedly, he was eager to get rid of the evil spirits. After his death, he was born again in Yokohama, Japan, and was attached to Sakura, Tsurumi. The story of the high school student Gao Zhonghao in the college, the story begins here…

- Description from Shubaow (Translated)