"Befall" is a verb that means to happen or occur. It is often used in the context of negative events, such as accidents, disasters, or misfortunes. The opposite of "befall" would be a verb that means to have positive or desirable outcomes. Some antonyms for "befall" could be "bless," "prosper," "succeed," or "triumph." These words convey a sense of success or good fortune, rather than the misfortune or doom that "befall" suggests. Using positive and negative antonyms can help to clarify the meaning of a sentence and create a more nuanced expression of thought.