Leonard against Hagler? He was 30 and had been out of the ring 3 years before that fight. I don't think too many people gave him a shot.

Also Duran against Iran Barkley? Duran was 38 and Barkley had just stopped Hearns in 3 going into that fight. Although I don't think Barkley had beaten anyone of note aside from Hearns prior to that and he went on to lose his next 2 fights. I'm not sure whether that one would really count