Ninja Gaiden...must of been said in 120 pages at least once.
I must of finished over 1000 games in my life, and, the last boss in that game was really hard.
Doom 3's last boss at nightmare is quite a pain, but nightmare isn't supposed to be balanced.
Castlevania 3 was the hardess versions of dracula, the first ones last boss was tough with no trick too.
Zelda's hardess, Link's shadow...zelda 2
Megaman, yeah rockman megaman 1 and last boss.
Bubble bobble? nah...but, princess tomato's last boss was one heck of a good paper, rock, scissors challenge.