Neurasthenia is a condition characterized by physical and mental exhaustion, irritability, and restlessness. Antonyms for "most neurasthenic" could include vibrant, energized, and lively. Neurasthenia often impairs cognitive function and causes a lack of energy and motivation. Antonyms that could describe the opposite of these qualities could be enthusiastic, motivated, and focused. Other antonyms could include calm, tranquil, and serene, as neurasthenia often causes excessive worry and anxiety. Overall, finding antonyms for "most neurasthenic" requires identifying qualities that contrast with lethargy, exhaustion, and a lack of focus or motivation.