The final confrontation against Count Dracula is a two-phase battle. In Phase 1, Dracula teleports around the room, appearing on one of the three platforms or on the ground, then shoots three fireballs in a spread pattern. The key is anticipating his teleportation and positioning yourself to hit him with your whip or sub-weapon as he reappears. The Holy Water is arguably the best sub-weapon for this phase; throw it on the ground where he is about to appear, and the flame pillar will deal continuous damage. Dodge his fireballs by moving between them or jumping over them. Once his health is depleted, he transforms.
Phase 2 sees Dracula as a giant, grotesque monster that moves slowly across the screen, occasionally jumping. His primary attack is to spit out three fireballs in a spread pattern. His weak point is his head. The Holy Water remains incredibly effective here; throw it on the ground in front of him, and the flame pillar will deal continuous damage to his head as he moves into it. If you have the Double or Triple Shot, this phase can be significantly shortened. Otherwise, whip his head, timing your attacks carefully to avoid contact with his body or fireballs. Stay on the offensive, but prioritize dodging his fireballs. Defeat this form to save Castlevania!