During the Dead City mission, there will be a total of 7 visions you must see for this achievement. While a few are in the direct path and therefore unmissable, several of them can easily be missed.
1. Playground - Unmissable
2. Piano Room - Once you reach the Playground vision, head through the hole in the ground. Coming out of the other side, turn around and look to your left for a building and the second one, the Piano vision.
3. Car - Head back through the hole in the ground from the playground, and coming out the other side head straight ahead down the street to see the car vision.
4. Empty room - Turn to your immediate left from the car vision and head into the building to find an empty room and a vision.
5. Family Looking Out Window - Unmissable, you'll need to pass this room to drop down to the next area.
6. Child on Floor - Going downstairs from the roof where the flying enemy is, make sure to look for a missable room off to the side where the child vision is.
7. Subway - Unmissable at the end of the mission
Check out the video below for a full playthrough of the game showing all collectibles, miscellaneous achievements like this one, and the Moral Points I obtained (I skipped a lot of them) in order to get the Redemption achievement. The DeadCity mission starts at timestamp
1:50:36.