what are specs of the PC?
Did you reset password here -
https://account.live.com/password/reset
Do you have a win 10 installer? If not, On another PC, download the
Windows 10 media creation tool and use it to make a win 10 installer on USB
So you get a black screen before the login screen or the login screen is black? Can you see the screen before it that shows a few icons along bottom?
If you do, we can try to get to safe mode from there. 1st we need to get to Advanced startup
On this screen click the power button
With the shift key held down, clcik restart button
Now if you can't access this screen, we need to use the USB to get there.
If you have an MSI motherboard, it might have Fast boot enabled, Need to turn that off before we can boot off USB
change boot order so USB is first, hdd second
boot from installer
on screen after languages, choose repair this pc, not install.
Both of these methods get you to the same place,
Advanced Startup
Now lets try start up repair before trying safe mode
choose troubleshoot
choose advanced
choose start up repair - this will scan PC and maybe fix this - will ask for logon info
if that doesn't help, we can try safe mode but if you booted up using a USB it may not show the startup options menu choice
choose troubleshoot
choose advanced
choose start up options
hit the restart button
choose a safe mode (it doesn't matter which) by using number associated with it.
Pc will restart and load safe mode