Remember that I work with computers for a living so have seen it all.
I really like Windows 10 overall. Some of the upgrade installs from Win 7 or 8 have been real problems. I always like to do a fresh install after they have been upgraded. Everything loads faster and the system is more responsive at the very least. Also, I see viruses and malware on 90% of the systems that I see. Often certain antivirus programs are more of a hassle than a help. AVG is one of the free ones that I see that needs to be uninstalled as the first order of business. PC Matic is a pay one and it is just about as bad. They sure make it look good in all those TV ads but that is where the good stops.
Installing system updates on a computer with corrupted OS files or registry errors can cause these nightmares where the computer goes into a reboot loop or or blue screens on start. Installing updates on a system infected with viruses can do much the same.
The best thing for this laptop is to wipe it clean and start over. Hopefully you have the data files backed up, otherwise you can remove the hard drive to extract the data, reinstall it, and start from scratch.