There was an Aussie in the early 2000's who won 11 from 11 but quit due to the demands of boxing being very stressful. Like keeping weight down as such. He then went to a life of crime. Got busted for drugs. I don't know what he did from there as it was 2 decades ago or so. Franky Gomez won 21 fights or so then quit. Smoking and alcohol got the better of him. More than a prospect though.
Wasn't Brock Jarvis in Australia too a bit overrated? I recently rewatched his fight against Marlon Paniamogan Pagalpalan the Filipino was going to finish him in the 2nd round. Honestly, outside of Australia he could have been stopped.