Undead status and Near Fatal attacks

Near Fatal is indeed just a visual effect. Cyclonic is a near fatal spell because it has a power of 15, which, when used in conjunction with the fractional damage flag, results in dealing 15/16 of a target's current HP, which will always put them below the threshold needed to cause Near Fatal status.

One potential way to counteract this is to give Near Fatal moves an element, and have undead enemies nullify this element. This comes with a whole bevy of issues, such as enemies being immune to these fractional spells without actually being immune to ID(Instant Death). Furthermore, enemies weak to this element would take twice as much damage(thus, if you make Cyclonic Wind element, something weak to it will take 30/16 of their current HP). Brave New World does something relevant here, in which most fractional damage is either Wind or Earth elemental, and having (essentially) zero enemies weak to Wind or Earth. You could do something similar to this...but it is a significant concession to make any way you slice it. As for a cleaner, more technical solution...that's out of my range of expertise.