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.