Antonyms for Firmness (opposite meaning)
WordNet sense 1 (not mentally or physically healthy):
unsoundnessWordNet sense 2 (the trait of being irresolute; lacking firmness of purpose):
irresolutenessWordNet sense 3 (the quality of not being steady or securely fixed in place):
unsteadiness, ricketinessFrom the ODE community, based on WordNetadd/edit