Over the years I have used the resources at 'Bleeping Computer'. They have their own scan tool that has been crowd-sourced that will do an exhaustive analysis of any Windows computer.
They also have a quite active volunteer community. The program runs and will provide you with a 'fix list' of problems found--but you need to know what you are doing since it is a powerful tool. If the fixes are straight-forward, you can do them and be done. If not...
After the initial scan if you have questions or concerns they ask you to post your results, and will offer help (quite technical) to clear your computer, but it can take a while for one of their volunteer mods to respond. But I have followed threads where the help is incredibly dedicated and thorough.
Here's the link to the initial scan tool:
https://www.bleepingcomputer.com/for...ery-scan-tool/
(Their website has been reorganized so it feels less familiar to me, but here's the forum that deals with infected computers:
https://www.bleepingcomputer.com/for...-removal-help/ )
The problem with relying on Windows Defender is that infections will often make their first step turning off Defender and/or stopping it from receiving updates--so the advantage of starting with the Bleeping program is that it will not be restricted or compromised in anyway by what may already be running on your computer.
Malwarebytes also offer a free trial of their service--download and install after the initial scan, and it will likely find a whole bunch more niggling bits of crap that you can do without.