When looking for alternative phrases to replace "best of all", one could use "most importantly", "above all else", "primarily", or "chiefly". Other options could include "top of the list", "first and foremost", or "at the helm". These phrases can be used in both formal and informal settings, making them versatile and useful for a variety of communication styles. Finding synonyms for commonly used phrases like "best of all" can add nuance and complexity to your language and help to keep your writing and communication fresh and engaging.