Wow this Battle sucks so hard. I normally play with the pierce gun but it’s super hard to defeat him with that. In phase two he will try to stomp on the ground to kill the lights and refresh his shield. Don’t let that happen. Get the scatter gun (shotgun) and be super aggressive. Levitate before him, so he cannot grab your ass. And when he talks about darkness and stuff hit him with shield burst oder throw something in his ugly face that pushes him out of balance and he will not regenerate his shield. Than do full power with the scatter and he should die easy.