>>712883608 (OP)Depends on the Duergar.
While trying to settle into the underdark some of them ran into conflicts with Drow cities who saw them as trespassing and, as Dwarves do, haven't forgotten and see any Drow as a possible surviving culprit or accomplice.
In other cases Drows and Duergar have indirect troubles from competition over slaves. A weird one, but with how troublesome things are below losing manpower can be a long term problem so they'd prefer the Drow dead and out of the way than thriving and making scarcities scarcer.
Ultimately though Duergar just generally have a contempt for everyone after being tortured by the Mindflayers without assistance from anyone.