not a final boss, but Devil May Cry 3's Angi and Rudra. Angi and Rdura is the reason a shit ton of people never even finished that game and those dudes were like the 4th boss and the HARDEST boss in the entire game. Also not a last boss but, Fire Leo in Viewtiful Joe 1... go to hell! That took me like 4 hours to do!
I do remember Alma being pretty tough in Ninja Gaiden way back when. I actually was never able to finish the game, but it was well past Alma that I got stuck and I don't think that it was on a boss fight. Demon's Souls has Maneater.... Maneater is incredibly hard if you have a melee oriented character because you can't hit…