The boss is (I think)
Coral-fueled SEA SPIDER
What loadout did you use?
I used
Plasma blade and pilebunker left hand. Laser rifle and vertical missile launcher right side. Reverse joint feets.
I feel I did not "get" this boss. The only reason I was able to win was because pilebunker charged damage output was insane. Everything else felt like it was tickling the guy.
I beat this one with a floating quad missile platform: two hand launchers, 8x vertical shoulder, 10x shoulder. Spending most of my time high in the air was the key to success.