Curaise and undeads

Update: Thanks to u/krissco, it's official: curaise is useless as a undead killer. It's a shame.

So.. if said undead is vulnerable to KO.. does it work like raise and deal NaN followed by your heroes jumping for joy?

Or does it work exactly like it does: instant KO, else deals holy dmg?

I wanna shatter my 4* Raise but need to know this first.. don't think I've seen info about it anywhere.

Edit: NaN not NAT