Alpha Breeding Pits Boss

Before I schizo rant, maybe I'm just bad at this game.

So I take 2 mate boosted, fully imprinted, ascendent saddled gigas to an Alpha Breeding Pits in the wastes. They we chew through everything mostly fine, pretty fun.

Then the boss shows up with ten minutes left, and I can barely damage him with my ascendent pump action, and my gigas barely tickle him. Do I need to chain bola this asshole or breed an army of fliers to kill him and that stupid bat?

Tldr I don't understand how to kill this boss.