The word "most unwasteful" refers to a level of efficiency and frugality that ensures minimal waste of resources, time, or effort. The antonyms for this term can be "wasteful," "extravagant," "inefficient," "profligate," or "lavish." A wasteful approach can lead to unnecessary expenditure, depletion of resources, and environmental degradation. Extravagance implies a disregard for rational spending and a tendency to live beyond one's means. Inefficiency suggests a lack of effectiveness in achieving goals, resulting in wastage of time and resources. Profligacy involves reckless spending without concern for consequences, while lavishness indicates an indulgence in luxury and extravagance beyond what is reasonable.