Feracity means the quality of being intense, fierce or burning. The antonyms of this word will be those that signify the opposite of intensity, fierceness or burning. Hence, the antonyms of feracity could be words like mildness, gentleness, calmness, quietness, peace, tranquility, placidity or composure. These words suggest a feeling of calm, peace and tranquility. To use these words in context, you could say that the soft sun rays were a stark contrast to the feracity of the scorching summer heat. The feracity of his anger was replaced by the calmness he felt after he took a few deep breaths.