The standard Windows Defender that comes with Windows 10 has been pretty good and relatively unobtrusive. Of course, one could make the argument that Windows 10 itself is malware, but I have my privacy settings locked down pretty much as hard as I can. I don't even use a Microsoft account to log in.
Then again, I only even really use my Windows partition for Overwatch these days, or web browsing in between matches. If I'm getting work done, I'll just switch over to Ubuntu.