In the UK, it would have to be Junior Witter. Probably the third biggest name in British boxing, and only 1000 people turned up to see his last fight against Viv Harris. On a World level, maybe Winky Wright, any heavyweight at present. Mayweather is unpopular, but still has lots of fans (i.e. ticket and PPV purchasers - whether they buy hoping to see him get beaten i'm not sure!)