The Meathead Potter
Sunny, a former bodybuilder and soldier who survived a World War III apocalypse and decades in an underground bunker, dies and reincarnates into Harry Potter at age seven after Harry is fatally injured by Petunia. The fused identity retains both Sunny's adult memories and Harry's childhood experiences.
The story begins with a hardened, survivalist, emotionally restrained protagonist shaped by war, bunker life, and abuse. Over time, he evolves into a magical powerhouse with a larger-than-life presence: physically dominant, combat-loving, increasingly carefree, and prone to laughter in the face of danger. His long-term personality trajectory is inspired by Monkey D. Garp.
The story starts slow. The first 17 chapters are about character building and early growth. The fun begins with chapter 18, when Harry is finally introduced to the wider magical world.
Expect no leaps in logic and a long journey.