I won Olympic gold. I was hyped as a heavyweight. I too was once 18-0. Yeah, I was a big guy too with a rep in the gym. In the amateurs, my chin wasn't as big of an issue as AJ's either. And then I got hit, and my career went south. Who am I talking about? Guess...
I woulda guessed Fraudley Harrison, but he was 19-0. And wasn't ko'd when he lost. Mercer was 18-0 then lost but it couldn't have been him, Mercer remained quality throughout his career.