Maybe a Fake Gintama - Chapter 36: The Uninvited Guy at the Class Reunion Is the Most Annoying! (Takasugi: Goodbye...)

Qin Tian accidentally transmigrated into a sickly body, a body with broken Dantian that was unable to practice Qigong, in another world. Fortunately, God had mercy on him by giving him a level up system. Useless? That was him in the past. Not worrying about practicing Qigong, he was now able to kill Monsters to level up. Easy! Level up when killing Monsters; level up when killing people. An unbeatable sovereign of the clan in the eyes of other people, but in his eyes, he is a glittering big BOSS.

With this level up system, he will no longer encounter any bottlenecks during a breakthrough in cultivation like other geniuses; all he needs to do was kill as many monsters, clan heads, sovereigns, world experts … to have a better life.

Dedicating his life on a road to become an expert.

- Description from Novelupdates

Miracles don’t come walking your way by themselves.

From humble beginnings, he ascended, overcoming every obstacle and living life on his own terms—until death took its toll. Yet destiny had a different design. Reborn into a world of greater splendor and majesty, he is granted a fresh start and boundless opportunities to rise again. This time, his journey begins from an entirely new vantage point, as he is reincarnated as the son of the most powerful woman in the universe. Follow his path of ambition and indulgence as he forges a new legacy and leaves his mark on an even grander stage.

He once stained the rivers and mountains with blood, his brilliance unparalleled. Unexpectedly, he encountered a great calamity, a dragon trapped in shallow waters, everyone thought he was nothing more than a useless son-in-law. But how could Gold Scales belong to a mere pond? The returning king, under the name of Frenzied Son-in-Law, with the War God’s stature, swept across the Eight Desolations of the Four Realms, the world trembled beneath his feet!