What you need is an orthographic Camera.
As you can see an orthographic projection doesn’t have any perspective.
For example:
This is my completely original Character Shmono from my completely original game Chrono Shwigger:
Let’s set him up with a “normal” Perspective Camera
Ingame it will look like this:
Now we simply change the camera to a Orthographic one in the Camera Settings
Which gives us this result:
The orthographic camera is what you want to use.
EDIT:
Here, one more comparision, this time with buildings.
