Anti-Climax Boss: Dracula. While he is hard, he's not the hardest boss in the game, and only has two forms with one lifebar as opposed to the previous game's three forms that had their own lifebars. However, it does take two or three hits to take down a single point of his lifebar.
Ghost dancer boss isn't that easy by itself, but by the fact that you can max out your health and whip in a room before the boss fight, and even if you lose, one of the walls contains the 1-up that will reappear after your death.
The omni-directional, flailable whip. Makes a joke out of most enemies, and it's your main weapon.
It makes the Axe, generally one of the better weapons since it hits flying enemies, practically useless. It should be pointed out that the omni-directional whip does not necessarily make the game easier, especially on the second loop.
The Cross plus a Triple Shot makes all bosses a joke. Quite tellingly, the secret invisible staircase right before the final battle gives you these exact powerups if you reach it.
It's Easy, so It Sucks: Due to the omni-directional Vampire Killer and the Jump Physics, some Classicvania fans deride this game for being too easy. This is the reason why every subsequent game has reverted to the less controllable jump from earlier games.
Nausea Fuel: Stage 4-3. The spinning background can make many gamers dizzy. Also, it lags.
Slogra. Every time you hit him, he leaps offscreen, lands on top of you and may or may not do a lunging attack that takes up way too much room. Simon is a Mighty Glacier and you spend the entire fight trying to keep your distance. When you break Slogra's lance you learn his beak is MUCH worse and he is more likely to lunge.
And as usual, Death. His mini-scythes are really hard to avoid and deal a ton of damage, as does every other attack in his arsenal. While you could stand your ground and flail your whip around to deflect them, they come out so frequently that you wouldn't have time to do anything else until he eventually comes down to try some other attack.
Luckily in this game Death does have one attack, where he stands still while drawing you toward him and twice throwing his reaper like a boomerang which movies slowly (and on the second throw doesn't even get all that close to you, since it's a fake-out), that leaves him vulnerable for a relatively long time. It's telling that even with such a weakness it's still a tough boss fight, even harder than the final boss.