Antonyms for the word "avoidably" are "unavoidably," "inevitably," "necessarily," and "compulsorily." These antonyms suggest that something cannot be avoided, controlled, or restrained, and must happen or occur regardless of efforts to prevent it. For example, when speaking about natural disasters, we would say that they are unavoidably bound to occur, as they are beyond human control. Similarly, when discussing aspects of life that we cannot change or avoid, we would say that they are necessarily a part of our lives. In summary, the antonyms for "avoidably" convey a sense of inevitability and inevitableness.