Hello.
In cases like the bearded devil who uses a glaive. It does not specify on the monster sheet that it does x3 for critical damage. From my understanding, unless otherwise specified the weapon in question will always do a x2.
https://www.d20pfsrd.com/bestiary/monster-listings/outsiders/devil/bearded/
However, on the weapon equipment a glaive does x3.
https://www.d20pfsrd.com/equipment/weapons/weapon-descriptions/glaive/
Which one is it? x2 or x3?