If you mean ATGs who were on the fragile side I nominate the obvious in Tommy Hearns. Wilfredo Benitez is considered great. His was average. I don't think he was fragile maybe by the end very worn and undertrained. Give me some time. I'm sure I can figure some out...
How do you go from RJJ, Wlad and Louis to Amir Khan? "ATG" would lose all meaning if that clown was ever considered great.
You got it Jm. Tommy Hearns got to be right up there. Unfortunately for him really but he still achieved greatness of course.
Maybe a controversial one but I'll say Juan Manuel Marquez, I never thought his chin was that good. But he had amazing heart and will power.