MTL - Full Marks Hidden Marriage - Chapter 5 Little Master found it.

The protagonist of the world where Lev Razanov lived had already achieved his happy ending. Meanwhile, the world continued to move forward. Until the protagonist betrayed humanity.[You have been killed by the main character.][Hero’s System successfully installed.][Do you wish to return to the past?]Lev was given a chance to return to a time when the story of his favorite novel had just begun.Although he was destined to become an extra villain—a pawn of the pawns serving the real villain, he vowed to end the lives of anyone who had caused him suffering.[Hero’s System inherits your desire from your life on Earth—the desire to do good.]“Who said killing your enemies is an evil act?”[You gain +10 kill points.][You gain +10 heroic points.]***Additional Tags: Second Chance, Past Play a Big Role, Game Elements, Handsome Male Lead.(Third Person Limited Pov.)

A young boy named Tang Jie was searching for a path into immortalhood when he happened to save an immortal in need, resulting in the latter owing him a karmic debt.

What? You want to repay me with mere Spiritual Enhancement Pills? Is that how cheap you view your life to be?

As a result, Xu Muyang ended up having to drag the brat with him.

You’ll never shake me off now, thought Tang Jie.

Frank, a mercenary known for his cold ruthlessness, decides it’s time to leave the bloody world of the underworld behind. But the underworld has no plans of letting him go. Relentless enemies from his violent past keep hunting him, and eventually, they succeed—Frank is killed.But fate has other plans. Instead of staying dead, he is mysteriously reincarnated into the body of a cop in a world filled with crime, corruption, and dark secrets. With the help of a strange, all-knowing system, Frank is given the chance to live again—this time, to prevent crime before it happens.