There are a variety of synonyms for the word "hardly", each with its own nuances and tone. For example, one could use "scarcely" to indicate a level of rarity or infrequency, or "barely" to suggest that something is on the edge of non-existence. "Seldom" implies that a particular occurrence doesn't happen very often, while "rarely" is similar but suggests that the frequency is even lower. "Sparingly" can convey a sense of limit or moderation, while "infrequently" is a more straightforward way to say that something doesn't happen very often. Ultimately, the choice of synonym will depend on the context and the desired effect.