If i am not wrong avast do have heuristic kind of thing with it.. 
this is not good to advice someone to use another AV or Anti Malware to remove some virus. If its true avast is less effective then why to use it ?
Because Malwarebytes is just a supplement to your main AV. Beside the free malwarebytes do not have real time protection. Malwarebytes specialises in rogues and other spyware. The user ask how to remove it, so I am just giving my suggestion as that is what I have been doing (for friends. How can avast remove it if it is not in their signatures? So te user need some way to remove that rogue.
Avast heuristics is kind of low (based on AV comparatives result) but I REALLY hope they improve this year. Avast is actaully quite effective (based on personal test-detection wise), it is very light on the system and I like avast so I am using it and recommend it to friends and family.
I am sure you are tired of hearing these, but in a day, 20000+ malwares appears and all AV are struggling to keep up. So no antivirus detects everything. As for me, avast detect all things I have thrown at it. So I have no problems and is one of the best in the market but there is still definitly room for improvement.Even the big names like Kaspersky and Symantec misses things too.
That is why it is important to educate yourself so you can avoid it. The best antivirus in the world is knowledge+common sense. I hope you are satisfied with my answer.