I've only got like around 20 (plus or minus two)
They are all easy to complete for the most part.
I have the hours of brawl left, all songs, 75 hidden songs, beat allstar mode with 10, and all characters, beat it on very hard.
The only really tough one I have left is Boss Mode on Intense. I beat the other difficulty levels already. You can complete the challenge with co-op. My friend and I have just been going two charizards and double rock smashing.
Also we managed to get roughly 51,000 feet total with all characters for the home run thing. Our longest co-op is around 4600 feet and our longest single is around 2300-2500 I believe. Anyone else come close to our distances?
Post your accomplishments and challenges you have left!