Windows Defender, which is built into Windows 10, is good enough for millions of people worldwide, including many members of AB. If you want to go for a third-party program, the most popular one among ABers these days seems to be Avast:
https://www.avast.com/en-gb/index#pc
(I used Avast for many years and still rate it highly. However, since getting the laptop I'm using to type this, I've never bothered installing it, as Windows Security seems to be doing the job well enough for me).
I can never see any reason to pay for anti-virus software, as the free stuff is just as good. However you need to top it up with an anti-malware program. The free version of Malwarebytes, or AdwCleaner (which is from the same company) is all you need if you're prepared to remember to run it occasionally, as it's 'run on demand only', rather than 'run in the background'. If you want an anti-malware program that's constantly running, then you need the commercial version of Malwarebytes. (I just us AdwCleaner though, which is free).
If you want to pay for a full security suite (although I think it's totally unnecessary to do so), these review sites are all trustworthy:
https://www.techradar.com/uk/news/best-internet-security-suites
https://uk.pcmag.com/suites-2/8400/the-best-security-suites
https://www.techadvisor.co.uk/test-centre/security/best-antivirus-3676938/
https://www.tomsguide.com/uk/us/best-antivirus,review-2588.html
Computer Active magazine (which I regard as an excellent source of information) currently ranks Kaspersky as their top-rated security suite. It's available at a discount through their website:
https://store.computeractive.co.uk/?act=details&id=34463