Phase 1:
To start the boss fight you must do the souls step at the dragon at spawn then go to the 115 meteor room and interact with it, after that the ground will start shaking and you have to go back to spawn and a engine charge up(the ones from revelations that you use to turn on the power) and godzilla will appear after that you must wait and when Godzilla does the big charge attack you must get behind the green tarp looking wall behind the ammo box and his attack will miss you(like the der eisendrache boss fight). You must go back to the charged up engine and fire it.

Phase 2: Godzilla will move to speed cola and the same thing will happen. For the charge attack you have to get behind the building that speed cola is on top of.After his charged attack finishes go back to the engine and fire at him again.

Phase 3: Godzilla will move to the rooftop where you build the sliquifier and for the charged attack this time you have to go behind the power house near where elemental pop is. After the attack finishes,fire the engine and you beat the map.