What is the best free anti virus?

The best free antivirus is YOU, just pay attention to what you download !

personally I think that avast is the best free antivirus, I used them before subscribing to mcafee

I'd personally highly recommend you to get Bitdefender.

It's a silent pretty easy to use Antivirus which doesn't really need any configuration tbh.
Does it's job really well and detects a lot!

It is best for you to use microsoft security essentials It is lightweight and easy to use and ensures you can protect your computer against malware.

I use Malwarebytes Free is not bad but if you have something to spend, you should take the Premium.
Other small tools I use is called:
hitmanpro
adwcleaner

I like the bitdefender free version, but the built in windows AV is also good now.

malwarebytes..............................................................

If you're looking for one NOT filled with absolute bullshit, Use Malwarebytes

i have a premium version of avira and ots very powrefull , i programm some "malware" (not very just troll app xd) and its detected lul

windows defender, with good habits
works for me, LOL