Akimbo Assassin
Earning the Akimbo Assassin achievement involves starting a campaign and shooting zombies. Use only pistols during the campaign. From the start menu, select "take a break." Allow the nonplayable characters to complete the campaign. When the campaign is complete, you earn the Akimbo Assassin achievement.
Cr0wnd
Change the difficulty setting to easy. Change the weapon of choice to a shotgun. Locate a witch and do not disturb her or turn on the flashlight on the shotgun. When the witch rises from her crouching position, aim and shoot the witch in the head. Killing the witch earns you the Cr0wnd achievement.
Dead Stop
Begin a campaign and select a shotgun. Locate a Hunter and run toward him while holding the LT button. Completing this task earns you the Dead Stop achievement.
Man vs. Tank
Select either Runway Finale or Dead Air. Change the difficulty to easy. Move through the levels until you reach the tanker. Place additional ammunition into the weapon and grab a Molotov cocktail or a pipe bomb. Complete the task, answer the call of the radio and start the pump. Move toward the right side of the plane and begin fighting the horde of zombies. Allow the Tank to spawn and move to the opposite side of the plane. Move back and forth without moving to the other side of the plane. Crouch down and shoot the Tank when he moves to your side of the plane. Completing this task earns you the Man vs. Tank achievement.
Helping Hand
Move into a safehouse and grab a shot gun. Fire upon and incapacitate the players on your team. One-by-one, revive each member of the group. Do not allow the other players to revive the incapacitated players. Reviving all of the players in the group earns you the Helping Hand achievement.
Unbreakable
Change the difficulty to easy. Grab a health pack. Select pause when your health is low. The players in the group revive your player. Allow healing and rejoin the game. Completing this task earns you the Unbreakable achievement.
Untouchables
Play the No Mercy campaign until level 5. Locate and climb to the top of the rooftop with the satellite dish on top. Move to the top of the building and locate the staircase. Move above the staircase and fire upon the zombies. When a zombie knocks down the door, move into the room with the survivors. When the helicopter lands on the rooftop, throw a pipe bomb and move quickly toward the helicopter. Completing this task earns you the Untouchables achievement.
What Are You Trying To Prove? and Zombicidal Manic
Allow a player to invite you into the last chapter of any episode of the game. The request must be from the dashboard. Completing the request earns you the "What Are You Trying To Prove?" and the "Zombicidal Manic" achievements. The person who invites you does not earn them.