Follow these instructions precisely. I will reference a trusted, community-verified 100% Dead God save file (available on GitHub user "IsaacSaveArchives").
: Often hosts resources for various Isaac versions, including fully unlocked saves used for practice. The Binding Of Isaac Repentance 100 Save File Download
A 100% save file (often called a “Dead God” file, named after the final in-game achievement) is a user-generated game save where: Follow these instructions precisely
: All enemies and bosses are fully recorded in the bestiary. Download Sources Trusted community resources for this save file include: The Binding Of Isaac Repentance 100 Save File Download
Once downloaded, you will have three files (usually named rep_persistentgamedata1.dat , rep_persistentgamedata2.dat , rep_persistentgamedata3.dat ).