And yeah, if it hits Accelerator and Aleister and they do nothing about it, it would erase them from existence, because they have no inherent resistance to such an ability.
Thankfully, the ability does visibly travel so they'd be able to dodge it with ease, among other things.
Why you bring up Iihiko who can be unaffected by powers he doesn't recognize (essentially power nullification), ORT who probably has some form of resistance to existence erasure, and Demi-Fiend who also has a similar sort of resistance given how Almighty attacks in SMT work, I have no clue.
All of these characters have an out against the ability in some way shape or form.
So like I said: either you have an out against the ability when hit by it or you don't.