For some reason It took me more than a year to complete this achievement because the game never counted most of the zombies I kicked off the roofs, like 1 out of 10.
I got this! Everytime I saw an enemy on a roof, I'd go out of my way to drop kick them off of it so I got this achievement early. There's another one "Judo expert" I think was the name, you had to grapple 50 enemies off a roof I think
