Great chins. Great fighters have them.

[Britkid]

Muhammad Ali to take the bombs of Frazier, Foreman, Shavers, etc.....

Larry Holmes had a outstanding chin.

I would say Holmes and Ali had brilliant recuperative powers, while a McCall or Chuvalo had 'great chins'. Although their chins were sound, Ali had issues with left hooks, and Holmes with right hands. But Ali always got up and it took a prime Tyson to beat a 38 year old Holmes, without a fight for nearly two years to keep him down.