Tearing to pieces is a phrase that expresses the idea of shredding or destroying something completely. Some synonyms for this phrase that can be used in formal or informal writing include "ripping apart", "shredding to bits", "pulverizing", "demolishing", "decimating", and "annihilating". Other alternatives may include "breaking into bits", "crushing to dust", "mangling", "obliterating", and "smashing to smithereens". Each of these phrases suggests a different level of violence or force, so it is important to choose the best synonym that fits the situation and tone of your writing.