Contract: The Dentist - The Big Bank
Difficulty: Online - Any
This achievement will require at least 1 other human player for it to be realistically completed.
From the start of the heist, you can go loud in order for lawenforcement to spawn. You'll need at least 1 player to remain in the lobby of the bank. Their goal will be to stay alive and communicate to the crane operator. The other player will go upstairs and access the roof using the emergency ladder. Once on the roof, build the zipline and zipline to the crane. Once on the crane, use the ladders to access the operator's room and interact with the controls, which will move the crane and begin to position Floyd the Pig. You will need to interact with the controls 3 times in order to position the pig above the glass roof of the bank. Now the player inside the bank will need to lure the police into the lobby of the bank just in front of the stairs in the center. When there is a police officer (any type) there, the crane operator will drop the pig, which will fall through the roof, into the bank, killing the police officer. The achievement unlocks for all players.
I recommend watching the video for the best explanation of everything that goes on in this mission and how to best set-up for it!
Note: This achievement is possible solo, but will require extreme luck as you won't be able to see the enemies. You can tie up hostages in the area shown in the video and hope that you get a kill as the hostages are being rescued.