When it comes to antonyms for "settles up," there are a variety of options depending on the context. In terms of financial transactions, some antonyms could include "defaults," "reneges," or "stiffs." These words convey a sense of failure to uphold one's financial obligations, rather than the idea of fulfilling them completely. Alternatively, if we interpret "settles up" as resolving a dispute or ending a relationship, some antonyms might include "escalates," "prolongs," or "complicates." These words suggest a lack of resolution or a resistance to coming to terms with a situation. Ultimately, the antonyms for "settles up" will depend on the specific circumstances at hand.