I ran into this exact issue with a corrupted MDF that SQL Server refused to attach. I first tried the standard DBCC CHECKDB repair options, but they either couldn’t fix the corruption or risked losing damaged data. I then compared a few recovery tools, including Stellar and Kernel, and eventually tried SysTools SQL Recovery.
For my case, SysTools was the most straightforward. It was able to scan the corrupted MDF, show the recoverable database objects, and export the recovered data to a live SQL Server database. What I liked most was that I could work with a copy of the original MDF without having to successfully attach the damaged database first. I’d still recommend taking a backup/copy of the original file before trying any recovery method.
So, based on my experience, if DBCC CHECKDB and your available backups aren’t helping, SysTools is worth giving a shot to repair severely corrupted MDF/NDF files.