There was a few different versions of Ronnie.
Light Ronnie in the years preceding 96-98.
Medium Ronnie was in 98-00 or so. He was just starting to push getting too big.
Big Ronnie aka Big Nasty was Ronnie in 03-04 where he just looked like an alien from a different planet. Huge and starting to really show signs of not being able to control that gut of his. He'd had the gut before, even in "The Unbelievable" but he was able to control it more than this period.
Then from 05 till his retirement he was just too big and his body was showing the years of injury and brutal training sessions (among other damages he'd incurred due to his supplement use). Having half a back, torn quad (minor tear not like Stubbs' quads), and just being too big with no way of turning back did him no good at this point.