This is a good way to level up a new character quickly until the infamy and influence costs become too high

First raise your reputation with Fortunata or any other reputation NPC to the highest level, then accept a mission from a contact.
Select that mission and then lower your reputation.
When you do the mission, the enemies will be set for your current reputation.
But the completion bonus will still be for the highest difficulty, giving you a lot more XP than normal.