He was great until 1999. And by great, I mean he exceeded all the criteria used to consider a bodybuilder a champion in the time period he competed.
After that, he made the ill-advised decision to increase the dosages and food intake to transcend mere "champion" status to "freakiest human ever" status. His physique therefore because unrecognizable from what it had been previously. Not entirely surprisingly, his physical decline after retirement has been equally spectacular as a result.