First of all, holy water doesnât burn sinners - who, in traditional Catholic doctrine, are âessentially every living beingâ anyway - it burns that which is by nature unholy, which is a distinct thing.
Since the Belmonts are presumably hurt by holy water as well, in a mirror match, and their bloodline presumably remains uncompromised by demonic or undead taints of any kind, we may therefore assume that either 1) some kind of demonic presence or aura - perhaps the âShadow Bugsâ canonically extracted from Mr. Game & Watch? - affects all members of the Smash Bros. roster, or 2) the vials are designed to ignite on any impact, not just on contact with the undead.
Second, everyone questioning why Pit or Palutena would be affected is a damned fool, as theyâre pagan entities and thus would have no immunity to holy implements and artifacts rooted in an Abrahamic religion, duh