Reborn: The Sword Immortal System Forces Me to Be Invincible

Su Chen, grandson of one of humanity's nine strongest, awakens the worst F-rank mortal iron sword embryo in his senior year of high school—utterly useless! No one knows that this scrap-iron sword embryo is actually the foundation of the supreme Sword Immortal Dao. Once he activates the Sword Immortal System, his innate sword intent reaches perfection, letting him permanently crush opponents above his level! You're a peerless genius? One sword strike crushes you. You're a demon clan overlord? One sword strike annihilates you. From high school campus to the border battlefield, the reborn Su Chen sweeps away countless enemies with a single sword, ascending to the pinnacle of world invincibility—the Sword Immortal Realm! — Description from novelcodex.org