Phase 1: Avoid square bullets with dodge, uppercut, and jumps. Attack with a few hits when he briefly stops. Phase 2: Pay attention to the ground. Quickly run or dodge right before his fist emerges. Attack when he stops. Phase 3: Wait until the homing crosshair shrinks onto you and dodge or run from it at the last moment. After Phase 3, attack as much as possible before the cycle repeats.