Nightmare was actually easier for me than I remembered. Got him on my third try, with plenty of health left. SA-X, on the other hand, killed me around a dozen times. The fight was really fun once I got the rhythm down, though, I didn't even mind dying as the final boss was in mid-death animation on my first attempt. Fun game to revisit, must have been at least a decade since I last played it. Have to echo the complaints about the limitations on exploration, though. I appreciate the attempt at a story, but it wasn't good enough to justify constantly locking areas, especially at the end of the game.