AV-TEST gave AVG AntiVirus a 100% rating for its protection against zero-day attacks during its May-June 2016 testing, for a start. It's reasonably quick to scan after the first initial pass, and the interface – ignoring the Zen bit of it – is super-clear and easy to use. Combine it with the mobile app and you can set it to scan and disinfect a machine without having to be close to it, which is a feature you won't know you need until it's too late.
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There are a few downsides. We're not super-fond, for example, of the level of permissions that AVG's Web TuneUp extension asks for – everything from 'read and change all your data on the websites you visit' to forcing your start page to AVG's own Yahoo-powered search engine – but that's an optional component.