This achievement is for killing the Pimp in Protect Tha Pimp 50 times. Protect Tha Pimp has 2 teams, one is the Pimp team which consists of one Pimp and the rest of the team must protect him as he reaches the goal. The other team are the hitmen who need to kill the Pimp before he reaches the goal. There are 5 rounds, each team will have 2 rounds where their team has the Pimp and the 5th round is random. ( to me it seems random, there might be a method to it but i cannot figure it out )
You will need a minimum of 4 people to start a match. Once the match starts the Pimp ( indicated by the purple hat they're wearing and pimp slap weapon ) will run towards the goal which is indicated by the blue square/triangle depending on if it's below you or not. The hitmen will the run away from the goal and meet the Pimp in the middle. Then simply alternate who gets the kill on the pimp, taking into account the 5th round until all your group has the achievement.
There are 3 maps in this gamemode and this is where each team should run.
Airport - Pimp will spawn at the entrance and should run towards the blue square on the map but stop when they go up the 1st set of escalators as there is 2 ways around and this will avoid confusion. Hitmen will spawn in a variety of places on this map and should run away from the blue square on the map.
Hospital - Pimp spawn on the top floor ( red walls ) and should run downwards. Hitmen will start on one of the levels below ( green walls is the bottom floor and blue walls the middle floor ).
Record Building - Pimp will start in the penthouse suites ( posh looking with red decor ) and should head downwards. Hitmen will spawn below them ( lobby/cafeteria are is the bottom floor and the office area is the middle floor ).
In general the stairs leading upwards on the map are in the north of the map so use this if you get lost on the map.