General assumptions: You must use all three disguises available in the sixteenth game mission.
Hope police officer disguise can be obtained only in the County jail stage. Attack any cop, for example one who will come to check the fire alarm at the beginning of the mission.
Agency grunt disguise can be obtained in the Outgunned and Hope Fair stages. It is best to choose a single target, away from other enemies.
Agency heavy trooper disguise can be obtained in the third or fourth stage. It is best to obtain it by attacking a sniper who is observing the market (Hope Fair stage) or one of soldiers exploring the first room in smoky warehouse (Burn stage).
General assumptions: You must find four evidences.
First evidence can be obtained in the County jail stage. You have to get to the other side of the main room in the county jail, collecting evidence from one of desks (you might use Hope police officer disguise to make things easier).
Second evidence can be obtained in the Outgunned stage. The secret lies in crates in the command center on the square in front of the police station and the easiest way to get it is when using Agency grunt disguise.
Third evidence can be obtained in the Burn stage. The item you're looking for lies on the trolley near the left exit from the main warehouse area. In order to safely collect this secret it would be good to use Instinct and throwable objects.
Fourth evidence can be obtained in the Hope Fair stage. You have to get to the mobile command center located on the other side of the market, near the exit door. Of course, it would be good to use disguise and Instinct.
General assumptions: You can't be spotted. In order to complete this challenge in 100% you have to do this in all five stages of the sixteenth mission. The most difficult stage will be probably Hope Fair, in which you have to skillfully move between covers and constantly monitor enemies' movements. Do not worry in the Outskirts stage, because the game will considered it as completed, despite fight with the sheriff.
General assumptions: You can't use disguises. In order to complete this challenge in 100% you have to do this in all five stages of the sixteenth mission. Same as with previous missions, completing this challenge is difficult, forcing the player to lower difficulty settings and eliminate some of enemies in aggressive manner. In Burn and Hope Fair stages you can make your life easier trying to run to the exit door.
General assumptions: Stun all policemen in the county jail.
This challenge can be completed in the County jail stage and despite appearances it is not particularly difficult, although it requires much patience and even more time. Remember that you can't kill policemen so you have to subdue each of them. In addition to cops, you'll probably have to knockout several civilians but it doesn't fail the challenge. Use crates and closets to hide bodies and remember to lure single enemies from groups with throwable items.
General assumptions: Kill all Agency soldiers in smoky warehouse, without beg spotted.
The opportunity to complete this challenge appears in the Burn stage. Your task is to kill all heavy troopers, while remaining hidden. I suggest playing on Normal difficulty setting and using disguise. Use garrote to eliminate subsequent targets and lure single enemies from groups with throwable items.
General assumptions: Take an Agency heavy trooper as a human shield and eliminate three more enemies.
You should start completing this challenge at the earliest opportunity, which is after starting the Burn stage. Choose any weapon, sneak up one of heavy troopers from behind and make him a human shield.
Now go to the main warehouse area and kill three more targets.
A Cleansing Fire
General assumptions: This challenge is automatically unlocked after completing the Operation Sledgehammer mission.
Surgical Precision Part 1
General assumptions: Kill three persons with headshots.
It is best to complete this challenge in the Outgunned stage, because in later stages you will encounter mostly heavy troopers and it is hard to hit them properly. I recommend using the point shooting, locating larger groups of Agency soldiers (screen above). But this is not necessarily required, because you can eliminate subsequent targets in more traditional way.
Surgical Precision Part 2
General assumptions: Kill five persons with headshots. This challenge is an extensive version of previous one.
Surgical Precision Part 3
General assumptions: Kill seven persons with headshots. This challenge is an extensive version of previous one.