i don't know about hardest cause i could post a lot of vids here but this one got some pretty retarded shit going on,and torfinho's told me his last trick was the hardest he's ever done.
i remember spending 6 or 7 hours on one trick in my s1 downhill video.but i've probably done even worse in pools.
i guess the hardest trick award would go to southcity or bullet,in the s2 dubs era.