I'm going to put my neighbor's dog's poop in front of their door
Why would you put it in front of their door?
I hate them because their dog poops in front of my door all the time.
Dog poop is rather unpleasant in front of your door, but revenge is not up to you, refrain from doing it. Instead, get together with the neighbor and explain what you want. Take a video of it and show them, they might start to actually walk their dog and pick up the poop.
If you think that's going to work, you are wrong.
I really think that you should just tell them about their dog pooping on your lawn. I'm sure they just don't know about it and that will rectify the situation.