Recognizing my margin of error and of BB’s propensity to use words when perfectly good numbers would do (a charming, yet clunky habit), maybe this nomenclature for toughness is better:
wimpy (1): IV.34
scrawny (2): IV.6, IV.36, IV.50
weak (3): IV.23, IV.35, IV.3, IV.12, IV.7, IV.38, IV.25, IV.48
decent (4): IV.53, IV.57, IV.2, IV.8, IV.52, IV.37, IV.15, IV.40, IV.27
solid (5): IV.5, IV.44, IV.33, IV.51, IV.64, IV.13, IV.43, IV.47, IV.62, IV.61
stout (6): IV.17, IV.45, IV.21, IV.19, IV.49, IV.26, IV.11, IV.24, IV.22
robust (7): IV.1, IV.4, IV.63, IV.18, IV.9, IV.39, IV.42
rigorous (8): IV.56, IV.59, IV.46, IV.31, IV.29, IV.16
tough as nails (9): IV.58, IV.60, IV.54, IV.30
Chuck Norris (10): IV.20, IV.28, IV.32, IV.10, IV.41, IV.14, IV.55