I don't know how underrated or otherwise it is, but I was impressed with In Jin Chi's losing effort against Erik Morales.
Yaqui Lopez seemed to always fight well, even when he lost. Obviously, his four title efforts were all excellent but I also thought he was doing pretty well against Michael Spinks before he got overwhelmed and the same against James Scott despite being widely outpointed. He's probably best known for his losses so not sure that they are underrated, really.