The antonyms for the phrase "most manic depressive," which refers to a severe mood disorder characterized by episodes of mania and depression, include stable, balanced, grounded, and serene. These terms suggest a state of mental and emotional equilibrium, in which an individual is not experiencing extreme fluctuations in mood or energy levels. People who are stable or balanced often have a consistent and predictable emotional state, which can make them less prone to mood swings or sudden changes in behavior. In contrast, those who are most manic depressive are often described as unpredictable, erratic, and volatile, which can create significant challenges for both themselves and those around them.