He had a great chin and also the heart to get back up after being knocked down. I thought he was done in the third fight against Moore but he managed to go the distance.
Going to the UK and taking the title from Freddie Mills by a KO should be considered one of his best performances.
He also "derailed" Floyd Patterson (although the decision was disputed), Bob Murphy, Danny Nardico, Paul Andrews, Bob Satterfield and other light heavyweight prospects.
I give credit to Maxim for his performances against Patterson and Robinson. He fought like a veteran against Patterson, more consistently although at times he was taking quite a beating from the much faster Patterson. The Robinson fight was not going his way but he withstood the extreme conditions and came out the winner.
Footage of the Patterson-Maxim fight: