What is an unholy nation?
If we go with the opinion of the average pretender its every nation but one.
If we go by consensus of pretenders its probably somewhat less than half of the nations.
If we go by modern majority its probably those who disturb the dead or kill people in the name of their god.
If we go by fantasy consensus its probably nations that uses 'unholy' priests or blood sacrifices.
You'll get more of the first kind. The second and third one as well. You will probably get less of the fourth one (the 'unholy', not the blood sacrificing ones). The distinction between unholy and holy priests is slowly dissolving. More grey zones so to speak.
BTW wich nations do you consider unholy in dom2?