Hardest boss...Jason, in Friday the 13th (for nes), after you kill him 2 or so times. He comes back and he's really pissed. You can fight him in 1 of two ways. 1, is inside the house of the his current victim.
But that's a bastard, as he moves side to side incredibly fast, so it's first off, hard to hit him. Secondly, if he does hit you, your life bar loses a very large piece of it.
OR! You could always fight him outside, where its just forward and backwards, not side to side. He's still really fast, and hits really damn hard, but at least you can't miss.
Never did beat that game...By the t