The antonyms for the phrase "sings praises to" are plentiful. One could criticize, condemn, denounce, censure or rebuke. These words are used to express disapproval, fault-finding or blame, whereas singing praises is all about expressing approval and admiration. Synonyms that might be used in place of "sings praises to" include laud, extol, acclaim, eulogize, or compliment. These words all have a positive connotation and suggest admiration and respect. However, it's important to note that in some situations, offering constructive criticism can be just as valuable as offering praise, so some of the antonyms should still be used with care.