I've beaten Castlevania once, but I've never been able to replicate that feat. The first four levels are fairly easy, but the 5th level with Death is just insane. Not only is he the hardest boss of the game, but you also have the Axe Knight/Medusa Head corridor right before him that'll kill you 4 times out of 5. And even if you manage to survive the corridor of death, you won't have any health left to deal with Death.
And of course, Konami somehow managed to make Castlevania III even harder.