I do not believe there will be one right answer.
Most famous anti-virus protections have the same or close to the same detection rate. Some free recommendations are Avast, Sophos Home, AVG, Avira, Malware byte, and 360 Total Security. Although I have used all of the ones I have recommended, I personally use Avast Free, not because it is any better detection wise, but because I like the GUI and simplicity of it.
Good luck finding your preference!