All undead and ooze are imune to crits. Constructs, most are imune - golems, marut, warforged have some fortification.
Also many high lvl boss type mobs which aren't normal imune to crits have some minor fortification.
And yea there is no prefix called chaotic. Chaotic is a alignment.
Theres 2 of them that do chaotic damage tho:
Ture Chaos - 1d6 to anything non-chaotic (must be chaotic to use)
Anarchic - 2d6 to lawful enemies (usable by anyone, but negativ lvls if used by lawful)