To crown all is an expression used to introduce the final or most important point in an argument or story. Synonyms for the phrase include "to top it off," "to complete the picture," and "to finish it all." Other related expressions include "to add insult to injury," which involves exacerbating an already negative situation, and "to be the icing on the cake," which emphasizes the added value or benefit of a particular event or occurrence. Each of these phrases can be used in a variety of contexts, and choosing the most appropriate synonym depends on the specific situation and desired emphasis.