So I got the Superweapon fight done. It's the hardest fight in the game so far: merciless bullet hell for it's rocket form, more bullet hell for it's robot form (yes, it turns out that CS!Omega's bullets can be made invulnerable) and Phase 3 being a final fight to finish off Omega itself.

Though among the toughest opponents in Gun, you are rewarded handsomely for this: A Golden HP Upgrade which increases your HP by 24 (which combined with the 75HP you'll have after getting all HP upgrades maxes out your HP to 99), the Cyanotype costume and the Will of Omega. Though just a novelty item for the most part, if equipped in certain situations, you'll be able to use the Omega Buster. It's the strongest weapon in the game and allows you to tear the final boss's HP down easily.