I think it would be like how a Lawful Good succubus is vulnerable to both Holy Word and Blasphemy.
That one is a bit odd actually, Holy word hits only nongood creatures and a the example succubus is in fact good. Said theoretical succubus should be immune to all of the Blasphemy variants.
According to the SRD, that's not so. Relevant quote and link: "Any effect that depends on alignment affects a creature with this subtype [the Evil subtype] as if the creature has an evil alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment."
http://www.d20srd.org/srd/typesSubtypes.htm#evilSubtypeBizarrely, this means that, for example, the aforementioned Lawful Good succubus would, if affected by the Fiendish Codex I spell Inner Beauty, receive both penalties and bonuses to her Charisma and Dex scores, negating each other; and cause BOTH area save effects around her. That's right, this would be a single-cast spell that does no harm to the target, but causes people within 15 feet to roll saves against both stun and nauseated.
A Lawful Good Succubus couldn't hold ANY Axiomatic, Anarchic, Holy, or Unholy weapons without taking a negative level, on a subject slightly more related to the original post, here.
Speaking of which, the "give someone a cross-aligned weapon so they take a negative level" trick is REALLY good with enchanted ammunition, and possibly ought to be included. A favorite of mine is +1 Holy Unholy Anarchic Axiomatic
repeating crossbow bolts. Play true neutral; load a case of those into your crossbow; and let people you don't like have opportunities to "borrow" or "steal" it from you; that'd be 20 negative levels for the aforementioned LG succubus; 10 for a paladin, demon, devil, or eladrin; Five for any neutral-and-something-else alignment. Quivers may or may not work all at once depending on your DM's interpretation of "wielding;" however, a crossbow is wielded, and the case is an essential part of the repeating crossbow, so in theory it should cause a negative level overload...
If you try this, be prepared to deal with wights. Lots and lots of wights.