The phrase "harsh reprisal" describes a severe retaliation or punishment. Alternatives to this phrase could include "merciless retribution," "ruthless vengeance," or "punitive action." Other synonyms for "harsh" could be "severe," "cruel," or "brutal." Similarly, synonyms for "reprisal" could be "revenge," "retaliation," or "payback." It is important to choose the right synonym depending on the context and tone of the sentence or passage. For instance, "merciless retribution" may sound more dramatic than "punitive action," but both convey a sense of severe consequences for bad behavior.