IPA: /ˌdaɪəˈbɒkələsnəs/
KK: /daɪəˈbɑːkələsnəs/
The quality or state of being extremely evil or wicked.
The villain's diabolicalness was evident in his cruel plans.
Diabolicalness → It is formed from "diabolical" (from Latin "diabolicus", meaning devilish or pertaining to the devil) and the suffix "-ness" (meaning the state or quality of). The word "diabolicalness" refers to the state of being devilish or wicked.
Think of the word 'diabolical' which means devilish, and remember that 'diabolicalness' refers to the quality of being devilish.