My 2 best examples are Chocolatito and Holyfield. They got everyone's best shot because their opponents almost always came into fights with them confident thinking they could win. I think that counts for something. I'm not saying you take credit away from for example Mike Tyson because most of his opponents came in to fights intimidated and defeated before they stepped in the ring. But mostly everyone Holyfield or Chocolatito fought gave a "Buster Douglas effort"
Chocolatito and especially Holyfield were both very durable fighters. But for a guy like Thomas Hearns or Amir Khan to achieve what they did with the punch resistance they had is, I suppose, more impressive than if they had the same attributes and better chins.