Yea, I think I made the captain a bit too hard. I'm curious to know if anyone had the nerve to defeat him (without cheating :D). You have to get lucky on the heals to get full hp and then nail the slash/stagger sequence:
2xA, 1xB, 1xA, 1B, reason for this being that his raycast in on his left gun, meaning that you can get more hits in when he staggers to the left.
Good luck and thank you for playing! :)