The phrase 'lightened burden' refers to the act of reducing the load or weight of a responsibility or challenge. While this phrase embodies positivity and relief, its antonyms, on the other hand, have a more negative connotation. Some antonyms for 'lightened burden' include 'heavy burden,' 'burdened,' 'weighed down,' and 'overburdened.' These words signify the experience of being weighed down, oppressed, or overwhelmed by a challenging situation. They are words that evoke a sense of heaviness, difficulty, and struggle. In essence, while 'lightened burden' brings to mind feelings of freedom and simplicity, the antonyms serve as a reminder of the trials and tribulations of life.