Larry Scott
I knew someone would say Scott just to be different but that is way off the mark. Scott was very dominant as the opposition at the time was relatively poor due to the low status of the contest for the first few years. But what's more, Larry Scott in the 60s had a truly fantastic physique and was a handful for anyone.
I think Columbo in 81 is a fair assessment of a guy who should not have won and showed a pretty poor physique. Danny Padilla should have had that show, with Platz and Roy Callender close behind. To be fair though, any of those 3 winning would have made sense. That has to be an example of a contest being fixed.