You must unlock every secret and achievement in the game.
This article covers everything: What a Dead God file is, the ethical debate surrounding save file downloading, how to install one safely, and why you might (or might not) want to skip the grind. the binding of isaac repentance dead god save file
Watch these guides for visual walkthroughs on achieving Dead God or managing your save files: You must unlock every secret and achievement in the game
for all 34 characters (17 standard and 17 Tainted). Complete all challenges . how to install one safely
If you’d like, I can expand this into a longer academic-style paper with citations, a formal bibliography, or a comparative section situating the Dead God save alongside similar artifacts in other games.