After seeing all the attack patterns, Billy realized that he could see the best moments where he could attack the ice golem. While that was also possible in fights that had just started, the accuracy and was pretty low, and the chance of failure was high. In any case, with the diamond glaive, all strike, no matter from which angle, would kill the ice golem. So, Billy would need something else.
In the split of a second, Billy saw the usual movement pattern that the ice golem used to try to smash him with both arms. When the creature put the left leg backward, Billy grabbed his glaive, and when the monster joined both hands, the weapon cut its head in two. The blast of the attack had been so powerful and fast that it even split the rest of the body of the creature as well.
You learned Heroic Spearmanship.