As much as I've heard complaints regarding McAfee, there is one thing that I can say about it that I can't say about a few others -- during the time when I was using McAfee, I'd never had an incident where a virus got past it. Eventually switched to products like Kaspersky, Bitdefender or Avira mainly because they offer comparable level of protection without loading down the computer as much. If there was any product that I'd had worse experiences than McAfee -- it would be Norton Antivirus. It slowed down the computer as much as McAfee but didn't offer much protection (frequently viruses would get through, and by the time it is able to detect it, it couldn't remove it -- so I often had to resort to extracting the drive from the affected computer, plugging it into my system and disinfecting using McAfee).
As far as antivirus product from Microsoft -- the one from several years ago didn't inspire much confidence as it passed through a lot of viruses that most other antiviruses would've caught.
As for all-time worst security software I'd ever seen, it would have to something for DOS called Watchdog (I don't remember the manufacturer). As an antivirus it was ineffective -- the computer would easily get infected. As if that wasn't bad enough, it would frequently thwart any attempt to disinfect by preventing the antivirus from scanning the harddisk --- even in administrative mode it would block access to executables as well as system areas (and there was no way to say what program should be "priveleged"). Frequently the only way to disinfect the system was to simply erase the harddisk and restore a clean image.