"Hath fling at" is an uncommon phrase that means to make a sudden, bold attempt at something. Antonyms for this phrase could include words like hesitate, retreat, or withdraw, which would describe the opposite behavior of being cautious or reluctant to take action. Other antonyms could include avoiding, neglecting, or ignoring, which would describe the opposite behavior of deliberately avoiding or disregarding a situation. Opposite words like these would suggest a lack of enthusiasm or courage, which would be the opposite of the boldness implied by "hath fling at.