How would you go about legally (i.e. the owner has asked you to, no wanton destruction here) destroying a multi story car park, using cars only (and possibly suicide drivers) - ie no explosives or such like. Is it possible on a practical level (ramming all the pillars, overloading the floors, etc etc? Perhaps you can think of some innovative ways (hence this being placed in IMHO).
Here’s innovative: Drop the cars from orbit. It’ll only take a couple impacts to flatten the structure.
Figuring out how to guide something that un-aerodynamic from orbit to an accurate impact is left as an exercise for the reader.
That rather feels like cheating to me.
Can the cars have plows on the front? That would help a lot.
ETA: However you do it, destroy the pillars starting from the inside, and work your way to the outer pillars.