Lennox Lewis was stopped by a Soviet boxer in the amateurs, by Valery Abadzhyan in the TSC tournament in Berlin in October 1986 (round 3 bodyshot knocked him down, he was hurt badly and the referee stopped it).
http://amateur-boxing.strefa.pl/Reco...n_Valeriy.html
It didn't stop Lennox from becoming a very successful pro.
I think Deontay Wilder has a very good future.