i still practice to beat the grim reaper still nothing.
I was running the game a little while back, and in the hall right before the Reaper fight my game crashed from having too many sprites on screen.
After that I actually switched over to the Famicom(NOT FDS) version where that bug was actually fixed,
the difficulty spike just afterward makes Grim look petty in comparison.
Personal recommendation, keep the throwing cross as long as possible, it absolutely wrecks everything, it's how I just barely took down Grim.