These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Castlevania I aka: Castlevania 1986
Anti-Climax Boss: While the first form of Dracula is insanely tough, his second phase is a joke—he merely hops around, trying to crush you, while you can basically whip him into submission quite quickly. If not by whipping, you can just use the Holy Water in the boss room to lock him in place.
Goddamn Bats: And Medusa Heads, and Ravens, and Fleamen.
Stage 16 (the start of the 6th area) has Goddamned Giant Bats.
Porting Disaster: The three home versions produced in 1990 are inferior to the original in several respects. The Amiga version, at least, gave us the great theme"Ecran Titre".
That One Boss: The Frankstein Monster and Igor according to some, the Grim Reaper according to others.
That One Level: Stage fifteen (block 5-3). Hello, excruciatingly long and difficult hallway filled to the brim with ultra-resilient axe knights and swarms and swarms of medusa heads. Hello, Grim Reaper. Goodbye, sanity.
And the stage after that has a swarm of Fleaman-carrying Altairs; they were difficult enough the last time you fought them, but now the space is much more cramped and you're moving vertically.