I've never read or watched the Harry Potter movies but that doesn't stop me from seeing evidence that Voldy would win. The only fanboy group here whose actually come up with feats that are relevant are the Harry Potter Fanboys.
Look Batman's my favorite DC superhero but please give some evidence before saying its a spite. Batman won't go to Fate, Constantine or any of those mystical people unless if he has knowledge of his opponent and no evidence has been given.
Since Batman hasn't ever encountered a killing spell, I doubt he'd know how to prep against one besides if Voldy can think a kill spell(like is said above) what is to stop him from just doing that on Batman at the beginning?
Until sufficient evidence is given, I take the position that Voldy wins maybe even in a spite. Come on Batman fans! Give me evidence to change my opinion!