I am persuaded that no AV can detect and remove some rogues. A good friend with Norton up to date got infected with a rogue. He is not one to click on something he does not know. He has no idea how he got infected.
The rogue would not permit him to download from the internet so he could not download and install MBAM or SAS.
I put MBAM on a disk, installed it on his computer, and with a Quick Scan it found and removed the rogue. Another friend had a similar experience and removed it with MBAM.
I believe Avast is one of the best AVs available, and AV Comparatives confirms that.
The fact that Avast did not catch the rogue is not an indication that Avast is not a top tier AV, but just that it cannot detect and prevent every bit of malware. For that reason I make sure that I run MBAM alongside any AV that I use.
Regards,
Jerry