Too damn hard.
It's just a simple shooting game. Shoot the lone opponent (who sounds really annoying) a ridiculous amount of times. You must also shoot each of his attacks before they hit you.
The health difference between you is astounding. You have to hit him so many times, whereas he can kill you in just a few hits. On top of it, the fight has phases. Each time you deplete his enormous life bar, it just fills back up. But you aren't so lucky.
I only got to the second phase, and even that was an extreme barrage. I couldn't block the "zero bomb" at all.
Overall, it's just way too hard.