irrevocable
Adjective
This word carries a heavy sense of finality and permanence. It is frequently used in legal or official contexts, such as irrevocable trusts or irrevocable mandates, where the law prevents a party from taking back a previous agreement. Outside of law, it evokes a feeling of helplessness or absolute certainty. While a decision might be "permanent," calling it "irrevocable" suggests that the mechanism for reversal has been completely destroyed or locked away, leaving no path back to the original state.