Akaimr Said:
"Can't login past login screen after trying to update software: When I login it loads little and it stops and say your computer restarted because of a problem ??? Before that I updated the latest software to macOS Big Sur from macOS High Sierra [...]the latest software didn't fully update it just kept on loading so I just stopped it and restarted the computer and try to login. Help"
-------
Reinstall the macOS:
Go Here: How to Reinstall macOS from macOS Recovery - Apple Support
Important: First, Back Up your Mac:
Create a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with the reinstall. Take this as a learning experience, knowing to always create a backup of your Mac, prior to making any major changes to it (i.e. update installation)