The Black Shadow Soul Hunter - Chapter 9 - 0: Soul of the ancestors

Hulk was a pro football player, a guy who loved nothing more than clutching a pigskin and barreling through the defense like a runaway freight train. He lived for the gridiron. But he never, in his wildest dreams, imagined he’d see a pair of nipples bigger than a football. He became a giant baby, reborn with a new name: Orion. Orion was the runt of the giant litter, the weakest of the bunch. But when he turned ten, something crazy happened. He saw a strange panel – that not only displayed his stats but also helped him level up. With the panel’s help, and a whole lot of elbow grease, Orion led his giant tribe to become the most powerful in the Barren Mountains. He went from zero to hero, becoming a mighty Titan King. He was no longer the runt; he was the top dog.

A teenager named Evan Mason was reincarnated into the magical world of Harry Potter and goes to school at Hogwarts!
With only his knowledge of the future and great talent for magic, he takes the path towards the top of the magic world, only to realize that ever step he took, changed everything!

- Description from Novelupdates

“I'm going out to do something, so I can't take care of you any more. You can go down the mountain and have fun. But if you can't find someone who matches your Innate Pure Yang Body in three years, you're finished!”These were the last words the old man, who was Lionel Yeager's teacher, threw to him before he vanished. Meanwhile, having mastered most of his master's skills, Lionel Yeager went down the mountain and took his first step into civilization for the first time in years.With his unparalleled medical and martial arts, he sets forth on a journey, befriending new allies and crushing all the enemies that stand in his way, as he attempts to resolve his Pure Innate Yang Body constitution, and cultivate to the top of the world!

The most feared Assassin in the world died because of vengeance.