Although I can't think of a specific battle name (I think it was a siege of Pavia?) but Pepin the Short's defeat of Aistulph is more influential than given credit for. Without the mutually beneficial alliance between the Papacy and the Carolingians which started there I don't see how Christian Europe emerges in anything like the same way it did after the papacy became safe and a temporal power.
The Battle of Vouillé in 507 under Clovis I was more significant. Had Clovis either lost, or had not converted to Catholicism from Arianism. it is quite likely that a decentralized Arian church would have become the standard in Western Europe
Not that it matters too much to me, as my Christology tends towards an Adoptionist viewpoint, not that Christology is a major concern of mine.