"Deal a blow" is a common expression that refers to striking someone or something in a way that inflicts pain or harm. There are several synonyms for this phrase, each conveying a similar meaning. Some options include "strike a blow," "deliver a blow," "inflict a blow," "land a blow," "hit hard," and "knock down." These phrases all suggest the act of physically attacking or assaulting someone or something and convey a sense of force and impact. Depending on the context, other synonyms such as "hurt," "harm," "damage," or "wound" may also be appropriate.