There are several synonyms for the phrase "blast away," which means to fiercely attack or criticize. Some options include "fire away," "let loose," "unload," "shoot down," and "lay into." Each of these phrases conveys a sense of intense energy and force in the attack. Other possible synonyms might include "hammer," "assault," "pummel," "rail against," or "tear apart." Depending on the context and tone of the discussion, some of these phrases may be more appropriate than others. However, each option embodies the idea of strong, direct criticism or confrontation.