Mac Mini Server starts to unreponsive desktop
Let us assume you've broken all the users, to fix that, connect a keyboard and display and hold S to start into single-user mode and remove the set up file.  Making a new user is non-destructive and it gets you a usable shall immediately with superior tools available to diagnose and fix the issue.


My MBP will not startup properly!


When you type halt, you can then start up the Mac and make a new local admin user with correct permissions and a working home folder. At that point you can evaluate whether to:


restore from a backup
make a backup
fix whatever was broken or try to narrow down what broke
wipe and start over


If you're someone who's going to make a go of fixing things in single-user mode, I would enable SSH login which gives you a bunch better error message when user home folder Sprague and also debility to do remote maintenance  in many cases where screen sharing brakes.