One of the worst corners I've seen was Tyson's in the Buster Douglas fight, that was shameful. I think Tito was let down by his corner in both of his losses, in the Wright fight they did nothing to help him.
I also think that whoever was in Luis Collazo's corner during the SSM fight let him down. How about giving your fighter some goddamn advice when he's getting his ass handed to him instead of calling him champ 20 times and then sending him back to get mauled some more.