This achievement is a hard one to complete. This is awarded for not only keeping Kidman alive but preventing Joseph from taking ANY damage. If he gets hit, you have to reload the last checkpoint. This is particularly a pain because you start pretty far away from Joseph to begin with.
You start at the top floor and he is below you. You can shoot from above but when you get the chance you want to be at ground level. What I did was pick off the haunted with my revolver and Joseph ended up running towards the other side of the map where you can join him on the floor. After that switch to the shotty and down them before they can get near Joseph. Haunted will start coming out of all the gates that are locked. They will emerge from the door on the left and then the door straight ahead(Facing the door you entered the room from).
There is a checkpoint half way through the battle. It will be when the haunted with Dynamite start appearing. You can use this to your advantage as they all spawn at the top initially. Go up on the pathto the top and they will rush you in a group because of how narrow it is. Shoot the dynamite haunted and make him explode taking out everyone else. There will be one straggler on the other side of the top area but I find the dynamite guys harmless at a distance. Once they get close they are a problem. Another group of haunted will spawn from the opposite side of the door that leads to the console that saves Kidman. They will contain two fat haunted so be careful. Once they are dealt with two more haunted will appear with dynamite. Take them out and you will unlock the cut scene that leads you to go save Kidman.
Run straight to the console and set the dials to what Joseph tells you to and bingo bango there's your mango!