Alucard is immortal, in every sense, he cannot die, nor can he age, he can pull an unending number of souls form just about anywhere in order to reform himself. Dante would be hard pressed to even so much as touch him as Alucard can move faster than the eye can see.
His immesurable accuracy with his handguns also beat Dante's ability with his guns into the floor, being able to hit a target square between the eyes while looking the other way and moving.
He can rip humans apart with easy, seeing as Dante's body is, in essence, human, when Alucard gets his hands on him, it's all over, so Dante has a healing factor, I'm fairly certain that our half demon can't survive being ripped to pieces.
He can even pass through solid matter, run up walls and hyponotize others to a degree, the fact is, Dante just dones't have the power to stand up to the true lord and master of Vampires, the fight would be over in a matter of seconds if Alucard went all out.
Though he wouldn't, seeing as Alucard likes to play with his victims, wear them down and let them think they have a chance of winning before pounding them into dust.