Strange thread title or concept, but I understand.

I nominate the Great Rocky Marciano.

5'10¾". Even for the 50s era, that's short for a Heavy.
Trained down to about 184 lbs.
Thin skin, prone to cuts.
Slow.
Awkward footwork.
1-dimensional.
No ability for fancy boxing or counter-punching, all he could do was come ahead and throw baseball type swings at anything he could hit, including at the arms and shoulders.
Very, very little ring-science in how this man fought.

^That's a lot of liabilities!
You'd wonder how he got into Boxing.

The God-given attributes he did possess:
Durability. Terrific Chin.
A Terrific right hand punch.
No fear of getting hit.
Tremendous Heart and will.
Endurance. Stamina. Part of that is genetics, but he also worked harder than anybody else to develop that endurance because he knew the other fighters had so many advantages such as height, weight, speed, timing, ring-science. He HAD to be in better shape than his opponents for his style to work. 15 rds of pressure and power that no one else could maintain.

And he was GREAT!