The phrase "double-trouble" is often used to describe a situation that is particularly problematic or challenging, but there are a number of antonyms that can be used to describe the opposite of this state of affairs. Some possible antonyms for "double-trouble" include "harmony," "ease," "simplicity," "clarity," "stability," "peace," "calm," "serenity," and "smooth sailing." These words all evoke a sense of peacefulness, tranquility, and contentment, and can be used to describe situations or experiences that are free from stress, conflict, or difficulties. Ultimately, the choice of antonym will depend on the context in which the phrase is being used, as well as the specific qualities that are being emphasized.