noun
implacability
im-plak-uh-BIL-uh-tee/ɪmˌplækəˈbɪləti/
The quality of being impossible to appease or soften.
Her implacability makes every attempt at reconciliation seem hopeless.

Etymology
Negating placabilis, “easily appeased,” yields the idea of being unappeasable. The noun ending makes this a quality: resistance to efforts to calm hostility or soften a response.
In context
Polly had adopted a policy of implacability toward her. She let nothing slip, forgave nothing, forgot nothing.
More examples
- The union's implacability leaves little room for compromise.
- She meets their pleas for mercy with cold implacability.
- His implacability surprises friends who remember his forgiving nature.
Forms
implacable adjective — Impossible to appease or make less hostile.
implacably adverb — In a way that cannot be softened.
Similar words
- intransigence
- Emphasizes refusing to compromise rather than resisting appeasement.
- inflexibility
- Suggests resistance to change, not necessarily anger or hostility.