I downloaded the free Avast to try out and I deleted it afterwards through applications. I tried downloading another one and it won’t let me saying avast is still on my computer… but it’s not… how do i completely remove it 
Try to delete the “/Library/Application Support/Avast” folder.
If you can’t find it, you can also try CleanMyMac X from the App Store.
Next time, you can find the Uninstall option in the tool bar under the Avast or Help menu. I believe at one point it was under the Help menu, now it is under Avast for me.
Hi I have same issue and this doesn’t work