This boss only has 3 attacks: A tail sweep, a purple fireball, and a dark-energy Godzilla blast thing. All three are telegraphed pretty clearly. The tail sweep can be avoided by keeping your distance. The fireball will hit the ground about half-way between the boss and the wall, then it splits in two and travels in both directions. Stand back a bit and then jump over it as it goes along the floor. The energy beam covers a big arc in front of him but this is actually the best opportunity to hit him. We you see him gear up for it come in close under his head and wail on him while the beam is going.