Whats the hardest official monster?

[Potato disciple]

A paladin focusing charisma can make most of Nocticula's saves (the highest beings a DC 44 fortitude) while still maintaining high to hit (charisma to attack from smite) and ridiculous damage (double his level to damage).
My vote is for Baba Yaga for being the highest CR caster enemy.

[The Sideromancer]

Potato disciple wrote:

A paladin focusing charisma can make most of Nocticula's saves (the highest beings a DC 44 fortitude) while still maintaining high to hit (charisma to attack from smite) and ridiculous damage (double his level to damage).

My vote is for Baba Yaga for being the highest CR caster enemy.

Given there seems to be a plot going that Nocticula is quickly approaching Chaotic Neutral, does this change the paladin-related part of your answer?

[Potato disciple]

Sure it does, but seeing as the trend is that she will ascend as soon as she hits CN, this won't really matter.