The word "most plotting" suggests a high degree of scheming or planning. Its antonyms would therefore be words that connote an absence or lower degree of such activities. Some possible antonyms for "most plotting" include "spontaneous," "unplanned," "unintentional," "unpremeditated," "unstudied," "improvised," "unrehearsed," "unconceived," and "impromptu." These words imply a lack of premeditation, calculated effort, or strategic thinking. They may also connote a sense of simplicity, naturalness, or authenticity.