Could mean there is a hardware problem; perhaps failed hard drive.
Were you able to check & see if Apple Hardware Test can start up?
• Using Apple Hardware Test - Apple Support
An authorized Apple service provider could provide further diagnostic to
verify the nature of the problem. An Apple Store genius (appointment)
may be helpful as they can provide basic checks & offer suggestions.
• Try safe mode if your Mac doesn't finish starting up - Apple Support
Did you try any other startup keyboard shortcuts to see if Safe mode or other
possible methods to access the system, and troubleshoot, were able to work?
• Mac keyboard shortcuts - Apple Support
...The suspicion of something out of the ordinary, from reading the kernel log,
comes to mind; the basic ones I've seen don't have a bunch of fffff's in them.
Sorry to not be of much (if any) help! 😐