If WinRAR says part4.rar is corrupt, you must redownload that specific part.
Multi-part RAR files work like a puzzle; you cannot open one without the others. Ensure you have all required parts (e.g., part1.rar through partX.rar ) in the . Beyond.Two.Souls-CODEX.part4.rar
If the game won't launch (e.g., Steam_api64.dll missing), your antivirus likely quarantined the crack. Restore the file from your antivirus history and add the game folder to your "Exclusions" list. If WinRAR says part4