Unalterably is the adverb of unalterable: in a way that cannot be changed, and permanently so. It attaches to two kinds of words. First, to a state or a verb of change — 'the accident unalterably changed his life', 'the town was unalterably altered by the flood' — where it means the change is one-way, with no road back. Second, and very commonly, to an adjective describing a fixed position: unalterably opposed, unalterably committed, unalterably convinced. That second pattern is where you will actually meet it, especially in politics, journalism, and formal statements — 'the government is unalterably opposed to the plan' announces that no negotiation will help. The word is formal, heavy, and somewhat old-fashioned; in speech people say 'for good', 'once and for all', or just 'completely'. A nice thing to notice is what a speaker gains by choosing it. Saying you are unalterably opposed does not describe the world — it makes a promise about yourself, and it dares the other side to try. Because of that, it often signals emotion under formal clothing. Note also that with a past event, unalterably usually points forward: it says the effect will last, not merely that the event happened.

不可改變地、堅定不移地。最常見的是 unalterably opposed（堅決反對），政治新聞用語。也可以說某件事「徹底改變、回不去了」。