The phrase "singing praises" implies the act of expressing admiration or approval of someone or something. However, there are a few antonyms that can be used to convey the opposite sentiment. Instead of praising, one could express disapproval or criticism. Words like "condemning," "criticizing," or "complaining" can be used to convey a negative attitude towards something. Similarly, words like "insulting," "slandering," or "belittling" can be used to express hostility or disdain towards someone. Antonyms provide a range of options for expressing different emotions and can help to add depth and nuance to language.