What? I thought the SA-X was easy as hell! If you go down to the bottom floor with it, and get into a certain timing with your jumps, you can dodge every attack it makes. I was able to beat it without taking any hits at all after the second or third time I beat it... No hard feelings though, I've had plenty of fights where I made a boss more difficult than it had to be (Ridley from Super Metroid, for one...) The hardest boss I can think of at the moment is Krool from DKC2, or just about any boss from Mega Man 2-3. Mind you, these are far from the "Hardest Boss", but at the time I was playing them (Age 4-9) they were pretty freakin' painful.