The infamy mechanic has been added as of Patch 2.5.1. It's supposed to work in a similar way to aggressive expansion in EU4, where by conquering provinces will contribute towards your infamy score which is represented by a percentage. If that score reaches 25% your neighbours will start to form coalitions against you.
But does anyone know whether Crusades or Holy wars will contribute to this infamy score?
If say, I'm France and a Crusade is called for Jerusalem and I'm the largest contributor therefore gaining all the provinces in the Kingdom of Jerusalem. Will all my Christian neighbours who also fought alongside me suddenly form a coalition against me because gaining all those provinces blew my infamy score sky high?
Or say I'm Castille and I start a Holy War for the Algarve. Is infamy constrained by Religion Group or will a Holy war against a different religion group increase my infamy also?
I've searched for some documentation on how the infamy mechanic is supposed to work but can't find any real explanation.
Best Answer
It appears Holy wars do affect infamy as would pressing any claim. However Crusades have no impact on infamy at all.
In my current game as the Emperor of Alba I declared a Holy war against the Sultan of Analusia for the Duchy of Beja in Portugal. Beja consists of 4 provinces and when I succeeded, enforcing my demands my infamy score increased by 33%. This led to to all of my neighbours (of mixed religions) within Hispania forming a coalition against me even though some helped me in my 'Just war'.
Note: There is an upcoming patch that will look to address the issue of unlikely coalitions ie. difference of religion and distance (so you should no longer see the Kingdom of Norway form a coalition against you with the Turkish Empire!)
Later in the game A crusade was called for the Kingdom of Anatolia. The Crusade was successful and I was the largest contributor gaining me the 20 provinces in Anatolia, which used to belong to the Byzantian Empire. This had no effect on my infamy what so ever.