The phrase "most prophetical" refers to something that is highly predictive or foretelling. Some synonyms that could be used to convey a similar meaning include "most prescient," "most clairvoyant," "most visionary," "most predictive," and "most prophetic." All of these words imply a sense of powerful intuition and an ability to see into the future in some way. Depending on the context of the sentence, any of these words could be used to replace "most prophetical" and still convey a similar sense of heightened foresight and clairvoyance. Ultimately, the word chosen will depend on the writer's intended tone and style.