The antonyms for the phrase "didst one's best" can vary depending on the context in which it is used. In general, antonyms for trying one's best may include not trying at all, slacking off, being lazy or careless, or intentionally doing a poor job. These words are often associated with feelings of frustration or disappointment, as giving anything less than your best can lead to unsatisfactory results. It is important to note, however, that not every situation calls for giving 100%, and there may be times when taking a break or doing only what is necessary is the smarter choice. Ultimately, the antonyms for "didst one's best" reflect a lack of effort or motivation, which can prevent individuals from achieving their goals.