The Incredible Hulk

Rather simple, destroy 25 cars, then heave their gray wreckage into buildings 25 times.

If you see the cars stick in the wall, or leave an impression in the wall it counts.

After haplessly throwing car after car at buildings and only having them occasionally stick I found the New York City Public Library (one of your landmark buildings on the map) seemed to accept every single car I threw into the lower area of the wall. This is a gray colored wall. I threw a bus, it stuck. I threw a limousine, it stuck, and even an ambulance stuck. The smooth north wall did the trick. I put ten cars in it and moved on.

So, if you are just trying to get this over with, go there, stick about ten in that library wall, save and quit, reload and repeat until it pops. Should be pretty fast for you as there are a ton of cars running by the library most all the time.