Smash Hit Achievement in Little Kitty, Big City

This is cumulative, and the only real objects you'll be breaking (to my knowledge) are pots around the various walls and ledges you'll be climbing and walking on. You'll likely make a bunch of progress without even trying, but if you make it a point to swat pots with  or as you explore and complete quests, you'll unlock this achievement well before finishing everything else.

For a quick grind, you can quickly do this by visiting the toy shop and smashing the diorama city (see Big Kitty, Little City (25G)). Then pause and reload your game to do it over again and again.