I use Avira as a complete offline scanner. Avira rescue cd is on a small linux distro making it completely offline.
Avast has the boot scan, and I haven't heard any complaints.
I have at least 4 different offline scanners on my multiboot drive.
Any kind of scanning is great if the virus was detected already by the company that scans. The virus or trojan mentioned above was not discovered until Dec 11.
https://www.virustotal.com/en/file/44fb2ae318a305108f9aba468e9a58d90aa695998cfeba9e951073edd69717fe/analysis/Even if that one is not actually a virus, still a scanner only finds old news. It's important but it's not everything.