Most notable example can be Super Castlevania IV, where zombie dogs, drop dead on the ground just to stand up a few seconds later. One of the secret rooms has a ghost of a dog running around, harming the player, when defeated, the ghost of an old man cries over its "corpse"
There are several instances of dead horses, whenether it's a skeleton of a horse as a boss, or horses heads that fly around both from Super Castlevania IV, or enemies that ride a horse that need to be defeated
The enemy Peeking Eye has an eyeball similar to that of a human. Some games have graphic death animation for it's defeat. Other than that eyeballs sometimes do exist as some sort of enemies, but their death animations aren't that explicit
Castlevania as a series revolves around the horror genre. Early Nintendo titles were under the censorship so there's little to no gore, however games on other consoles are not afraid to show it
Castlevania: Rondo of Blood has a playable charachter of Maria Renard, who is a small girl. When one takes too much damage, she faints. Canon wise, she does not die and manages to survive events of Rondo of Blood and Syphony of the Night
As much as the series like to be creepy, audio gore is not that common, although there are some notable exceptions like the Granfaloon boss in Symphony of the Night, or the bloody waterfall in Harmony of Dissonance
There aren't much direct scenes of hanging (with the exception of Alucards Nightmare in Symphony of the Night), but some backgrounds can show hanging skeletons, or people
in one of the cutscenes of Rondo of Blood, Dracula enter the cell of captured Anette. As he comments on tasting her blood she pulls a knife to her nech and threatens to kill herself
Not on screen, although the big part of the lore is Lisa being executed for being accused of being a witch. This angers Dracula and makes him rebel against humanity, all while his son Alucard, sides with humans just as his mother wished him to in her final words
in Symphony of the Night Richter Belmont is revealed to be under dark Priest- Shafts influence.
Harmony of Dissonance has a charachter Maxim which influenced by Dracula's remains develops a split personality
in Castlevania Circle of the Moon Hugh Baldwin gets influenced by Dracula due to his jealousy
Not really, although the opening scene of Castlevania: Circle of the Moon has a bit where Dracula makes two vampire hunters fall down to the catacombs, which they survive perfectly fine. The very first Castlevania, Castlevania Legends and Castlevania IV also feature the trope with falling through the falling floor but no one has ever canonically died this way
In order to fully resurrect him in Castlevania: Circle of the Moon, Dracula requires a sacrifice. As three vampire hunters enter the castle, two of them fall into a trap and the third one gets captured for the ritual. Castlevania: Rondo of Blood has four maidens that are captured and need to be rescued
Lore-wise, no one has ever canonically drowned in the Castlevania universe. In practice- Simons Quest have bottomless pits with water, that are instant death when jumped into