The term most onward is a superlative expression that means to proceed or move forward more than any other direction. When looking for antonyms for this term, the opposite would be anything that opposes, retracts, or goes backward. Words like "backward," "reverse," "retreating," "retrograde," and "backsliding" could be considered antonyms for most onward. These words mostly denote a way of withdrawing or failing to progress in some way. Some other possible antonyms for most onward could be "stationary," "frozen," "idle," and "stagnant," all of which convey the idea of being static and not-actively-moving forward.