This guide will teach you how to do the "What Are You Trying To Prove" achievement easily.
I'll teach you how to make the "Zombicidal Maniac" and the game's most difficult achievement (If you try to do it normally), the "What Are You Trying to Prove?", But there's an extremely easier way for you to make this achievements, which is how I'm going to get you teach now.
You and the players who want to earn the achievement need to be in lobby and start a campaign on the easy difficulty, you need to run to reach the last safe room.
In the last safe room, don't open the door, start a vote to go back to the lobby
In the lobby, put it in the last chapter of the campaign you were doing, but in the expert difficulty.
Now, you will need to play the finale on expert, this is the most complicated step, however, there are easy ways to pass them, whose I will also explain now.
In the building where the radio to call the rescue is, there is a ladder at the end of the room, 2 players are at the bottom and 2 players are at the top, when a Tank comes, everyone leaves and take great care not to to be hit, as soon as he is killed, you go back to the ladder, and as soon as the second tank is killed, you run to the place where the helicopter will land, to be easier, one of the players needs to have a pipe bomb, to protect others.
At the far left, looking to the side of the pier, there is a low stone where all players can climb, while they are on that stone, they are immune to almost any infected and tanks (Except smokers, hunters and boomers), and tanks will automatically die, the Sometimes even one or two infected people can reach you, when the ship arrives, you go to it by water, at least one player will need to have a pipe bomb to distract the zombies, and so you go to the ship.
There are 2 ways to make this finale easier:
In front of the yellow stripe, there is a huge open space, which makes the visibility of the zombies much easier, which will come practically in straight lines, as for the tanks, you can rotate around the airplane to make it easier, and as always , when the plane door opens, it will be easier to go there if a player has a pipe bomb.
There is a baggage box behind the truck where you can push using gallons or propane or oxygen tanks, push this box close to the left wing tip of the plane (Seeing in front of it), so you and the players will be able to climb in on top of the plane, which also makes you immune to almost everyone infected, except smokers.
At the edge of the map, there in front of the farm, there is a half-destroyed fence, if you climb on the left part of it and jump in the hay, you will see that there is a kind of invisible path, walk forward and try to jump on the mountain, maybe you will take some minutes to get the hang of it, because this invisible path is narrow, but as soon as you take it, go CAREFULLY to the left until you find the mountain limit, which will have a tree, you and the other players need to stay close to that tree, so you stay immune against all those infected, as soon as the rescue arrives, as always, a player will need to have a pipe bomb to facilitate the trip to the vehicle.