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?
It could be an editing error--every other glaive-wielding monster I can find in the Bestiary has the correct x3 multipler. Or it might have been intentional--their glaives are already special in that barbezu deal infernal wounds with them, so maybe the critical multipler was dialed back as an act of balance.
If you're in strict RAW-land, it's x2, as that's what the monster stat block lists.
My guess would be that the (1d10+6 plus infernal wound) for damage messed them up, and it was an oversight.
(1d10+6 plus infernal wound/x3) would be how it should be written, I believe, but that looks weird. It seems pretty clear to be from the rest of the stat block that it is intended to be a normal glaive.