Return of the Unrivaled Spear Knight - Chapter 17

Waking up, I discovered that I had become a cat with superpowers...

In a post-apocalyptic fantasy world layered into multiple realms, humanity faces extinction due to their endangerment of the main realm. Forced to merge all realms back into one, a deity grants humans a leveling system to empower them, lest they become extinct when facing the mythical creatures. Noah, our protagonist, embraces the role of a monster tamer, trading his humanity for strength and eventually transforming into a monster himself. As Noah struggles with his evolving identity, he must navigate a world where the line between human and monster becomes increasingly blurred.

When a person dies, they either die light as a feather (aka unimportant) or heavy as Mt. Tai (aka very important).