When it comes to expressing disapproval, there are many phrases that can be used as synonyms for "criticizes severely". Some of these include "rebukes strongly", "condemns harshly", "castigates severely", "denounces vehemently", "reprimands severely", "scolds harshly", "lambasts mercilessly", "censures sharply", "disparages severely", and "berates vehemently". All of these phrases suggest a level of intense criticism or disapproval, and can be used in a variety of contexts, from personal relationships to professional situations. Depending on the tone and context of the conversation, any of these phrases can be effective in conveying a message of strong disapproval and holding someone accountable for their actions.