Part One: Preparation
Since there is no way to actually start in the church, make sure you spawn in either the safe house or the main starting square outside of the large mansion. None of the disguises you can spawn in with will help you here, so there is no point wasting time in trying to slip out of the mansion unnoticed. We decided to complete this kill with the minimum level gear since not everyone will be Rank 20. Once you exit the safe house make your way down to the church and head towards the morgue on the far end. The church is heavily guarded and this seems to be the weakest point of entry, as the church staff member is left unguarded at the front desk.
Enter the morgue, shut the doors behind you, and knock him out. Make sure to pick up his church key, take his disguise, and drag him into locked room behind you. Hide the body next to the corpse on the table and carefully exit the side door. The church staff disguise is not immunity, as any other staff members and the main priest will be able to see right through it. Always avoid the church staff’s line of sight and if you are getting spotted duck behind some cover until they leave you alone.
Thankfully, neither the bodyguards or the cardinal will be able to identify you in the church disguise, so moving around them will not raise any suspicions unless you head to the basement. Once in the chapel, hide behind a pillar or in the confession booth, just make sure the staff member on the balcony doesn’t see you, and wait for the regular priest to show up. Him and the cardinal will talk for a moment and then will head into the basement. Slowly follow them downstairs, but instead of going into the actual cellar, hang a left and enter the security room.
For whatever reason nobody goes into this room aside from the priest, so quickly destroy any security camera evidence and just wait by the door. Eventually, the priest, cardinal, and his bodyguard will finish talking and disperse. The priest will leave first, so make sure to knock him out and drag him into the security room. There are no places to stash the body, but since he is the only person who goes into this area you don’t run the risk of being seen. Now that you have a location, it’s time for your hitman to execute the target.