unalterably

/ʌnˈɔltərəbli/
adverb
  1. In a way that cannot be changed or modified.
    • The landscape was unalterably transformed by the volcanic eruption.
    • She was unalterably opposed to the new policy, refusing to consider any compromise.
    • The past is unalterably fixed, no matter how much we wish to change it.
Antonyms