Are some enemies immune to the Ring of the Lucii?

Solution 1:

According to the wiki, instant Death is ineffective against some enemies, while Alterna has a random chance to miss.

• Death:

Some rare enemies are immune to the instant death, but even most bosses are susceptible.

• Alterna:

There are no enemies that are immune to Alterna, but the chance of it working is random and Noctis's Magic stat doesn't appear to affect it.

After the 1.06 patch it has a chance of working even against superbosses and story bosses such as Adamantoise, MA-X Angelus-0 and the penultimate boss. The patch also improves the overall chance of it working on any enemy.

The Holy spell seems to work on all enemies, as the wikia does not mention any immunities.