Dragon Tomb Guardian

First, a disclaimer: this book has a few problems at the beginning, but later on it becomes a full-on invincible-protagonist story.

Crimson flames blazed across the scorched earth, and the clouds of war shrouded the entire sky. Nidhogg, the powerful cursed dragon and a walking calamity, hovered silently in the air. Behind it, countless gigantic shadows appeared in the distance, and the aura of death spread without end.

"So, how exactly did I end up here?" Its enormous claws scraped against its chin, scattering sparks, as Nidhogg fell into thought. "I only wanted to be a quiet guardian of a dragon's grave. How did things turn out like this? Hm, this has to be the world's fault."

Hesphia, Goddess of Creation: "No way in hell am I taking the blame for this."