If only is a phrase used to express regret or a wish for something that could have been different. There are several synonyms for if only that can be used to convey the same sentiment. Some of these synonyms include "only if," "had only," "wished for," "regretfully," and "unfortunately." These words and phrases can be used to express longing for a different outcome or a different past experience. Additionally, these synonyms can be used to express a sense of disappointment or discontent with the present state of affairs. The use of synonyms for if only can add variety and nuance to one's expressions of regret or longing.