The Omega Pirate is a case of "Good boss theme; bad boss battle".
I had SO MUCH trouble with the Omega Pirate because I didn't have Ice Spreader. I died more times than I had died on any other boss. Meta Ridley was easier and so was the final boss. SO WHY WAS THE OMEGA PIRATE SO MUCH HARDER!?!
That said, his boss theme is a banger.