"unappeasable" in the adjective sense
1. grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting
not to be placated or appeased or moved by entreaty
"grim determination"
"grim necessity"
"Russia's final hour, it seemed, approached with inexorable certainty"
"relentless persecution"
"the stern demands of parenthood"
Source: WordNet® (An amazing lexical database of English)
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