If you need to demolish 3D buildings in your virtual project nicely and easily, you should take a look at a6oo's voxel and Constructive Solid Geometry (CSG) building system for destructible cities in Unity.
The tool is not ready for download yet, but you can already see how impactful and natural it is. Construct a building and get some holes in it, watching the chunks peel off satisfyingly.
The creator is planning to make a demo so anyone interested can try the system out and then put it up as an asset, so stay tuned and check out a6oo's other creative projects on Reddit: