Bofuri (The Strongest Shield Of Tensura) - Chapter Seventy Three

“What kind of guardian would you want to be? the one who destroys everything or the one who protects everything?”

Jason, one of the many casualties during a nuclear explosion gets the chance to reincarnate into another world due to his deeds during the war.

He gets tossed to another world due to ending up with the Shadow god as his patron, something deemed impossible.

With a system to guide him in the world of Clover and a family jinxed through the generations, his adventurous life in new world begin.

An ordinary student, a wretched peeper, a cowardly teenager with a kind heart. In a terrorist attack, he inherited the knowledge of countless elites, embarked on a path of God Jagged Tu…

He is an artist!

He is a mathematician!

He is a psychology Doctor!

He is a master of fighting!

In fact, he is a man

Taken off raw site:

A wretched, dirty young man is working during the summer when he was caught up in a mysterious explosion. After that explosion, the young man is then left with the memories and knowledge of dozens of the world’s experts.

He has changed, his heart has become cold, iron-blooded. He became a killing machine, his mind turned mechanical, calculative. Everything goes according to his plans and calculations!

In this magical, slaughterous world, a door is opened for him…

- Description from Novelupdates

At the end of the world, a legendary hero gave his life to save a dear friend, only to be reborn as a four-year-old orphan with 'Crab Affinity'.The apocalypse has come and gone, claiming humanity with it. All humans have had their 'Souls' stolen and claimed by monsters - vampires, demons, zombies - you name it.Reborn as Barnacles (Barns for short), the once-legendary hero claws his way back to strength under the tutelage of the gluttonous King Crab, a sentient crustacean with more vice than virtue in his shell.Follow Barns' journey as he rediscovers his power of rebirth, which when combined with a little 'crab magic' has the power to reset humans back to their original selves.It's time to take a crack at resetting the apocalypse.

Zhang Gong decides to learn light magic, a magic few show interest in and eventually becomes the legendary Grand Magister. While trying to end the continent’s east and west separation in order to unite all of the different races, he becomes every race’s Child of Light.