Well, if Christianity is true in the Castlevania-verse, then Alucard could be completely screwed. Not sure if Jesus' blood sacrifice applies to half-vampires but the drinking of blood outside of the symbolism of drinking Jesus' 'blood' is condemned in multiple passages such as:
"Leviticus 17:10-14
“... I will set my face against that person who eats blood and will cut him off from among his people. For the life of the flesh is in the blood, and I have given it for you on the altar to make atonement for your souls, for it is the blood that makes atonement by the life.
1 Corinthians 10:21
You cannot drink the cup of the Lord and the cup of demons. You cannot partake of the table of the Lord and the table of demons."
He's arguably doubly damned because he also willingly and unrepentantly practices dark magic. White magic and black magic are not acceptable in Christianity:
“Let no one be found among you... who practices divination or sorcery, interprets omens, engages in witchcraft, or casts spells, or who is a medium or spiritist or who consults the dead. Anyone who does these things is detestable to the Lord...” (Deuteronomy 18:9-14).
Paul in Galatians 5:19-21. “Now the works of the flesh are manifest... witchcraft... and the like. I warn you, as I did before that those who live like this will not inherit the kingdom of God.”
In other words, without being saved through grace AND repenting of sins such as performing magic- the magic that they use to thwart evil and save lives and almost certainly do NOT believe they should repent for using in their hearts- Alucard and all other spellcasters in the series are damned to Hell by default... and I was going to put a smarmy remark about how supposedly loving the Christian god is here, but I decided not to... oh, wait... >_>
Alucard also consulted prophecies and worked to see them fulfilled, which is also apparently detestable. Kind of weird considering the Book of Revelations... XD
On a side note, if Alucard dies in-series, fans are going to throw a fit.