When it comes to describing promptness or being right on time, numerous synonyms for the word "timeliest" can be employed. For instance, the term "punctual" refers to someone or something consistently acting promptly and reliably. "Prompt" is another fitting synonym, emphasizing being quick to act or respond without delay. Similarly, "timely" captures the notion of an action occurring at the right moment or within an appropriate timeframe. Additionally, one can use "expeditious" to convey the sense of efficient or speedy execution. "Immediate" is another synonym that implies happening without any delay or hesitation. Overall, these synonymous words aptly capture the essence of being timely and prompt in various contexts.