Anti-Climax Boss: Dracula. While he is hard, he's not the hardest boss in the game, is easier than his version in other games, only has two forms with one lifebar as opposed to the previous game's three forms that had their own lifebars, and his "second form" is just his normal self without his mask on, while the only new attack he gains in that "form" is an easily-dodged lightning attack. 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.
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.
Hype Backlash: The game was very highly received when it first came out, introducing a multi-directional whip and fully controlled jump physics. While these were welcome additions, in later years the lack of difficulty, somewhat simplistic level design, bosses that can be defeated by just mashing it out with them with no regard to strategy, and containing some areas (most gratuitously the spinning room) that feel more like excuses to show off the console's graphical tricks than benefit to gameplay has caused its praise to wane quite a bit. It's still fairly well-regarded among the Classicvania games, but more fans have started to recognize games like Bloodlines and especially Rondo of Blood as being far better titles.
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. Additionally health-restoring powerups are a lot more plentiful and easier to find, you can sustain a lot more hits before dying, and enemies are generally weaker in this game, dealing less damage and taking a lot less hits to kill, including even the Axe Armors that are Demonic Spiders in other games, exacerbated by how powerful your Whip is in this game. Then there's the bosses, which tend to be a highlight of the other Classicvania games and can be murderously difficult, are very weak in this game, when you can defeat most of the bosses by just mashing your Whip at them with no regards to dodging their attacks, killing them before they're able to kill you as long as you made it to them with enough health (which with the aforementioned sustaining less damage from hits and plentiful health powerups, should be the case most of the time). Even the harder bosses like Death and Dracula pale in comparison to their versions in other games.
Nausea Fuel: Stage 4-3. The spinning background can make many gamers dizzy. Also, it lags.
Scrappy Mechanic: Oddly enough the omni-directional whip, despite it averting Denial of Diagonal Attack and giving the player ultimate control over their weapon. The main reason is that it pretty much obsoletes the subweapons other than the Cross with a Double/Triple shot, when subweapons are seen as a crucial part of the Castlevania gameplay. The Axe in particular gets made useless by the Whip when the Whip eliminates its main usage of hitting enemies above you. Additionally the Whip, your basic weapon, being so powerful is a large part of why the game is a lot easier than other Classicvanias, especially when the enemies and bosses were made a lot weaker in this game.
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 moves 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.