Unfortunately there doesn't seem to be any way to tell when maximum damage has been done. You may be missing some destroyable object and not even know it. That being said, a few good rules of thumb are as follows....
- Have both characters use their Super Move
- Use every interactive object (these can be found in the guides for the 'Groundbreaking' achievement
...and a couple my predecessor missed that definitely help
- Make sure you use all the level transitions (see guides for 'Around The World') achievement
- Try to split your fighting up, and make sure to cover all possible ground. Don't just stick to one corner.
Do all of this once in each stage and you should have your achievement in no time.