I would have to say the trail that starts at Wilhelmina and ends overlooking the Koolau. I ran out of food and water and was getting delirious. .. second runner up is the trail behind Helemano plantation (Sorry, I don't know the name of this trail too).. we had to 4x4 to the trail then it was super muddy and we saw wild pigs. Yikes!

I did a hike at Mariner's Ridge. I'm not an avid hiker, but this one was pretty tough....

i would have to agree that the Wilhelmina one was difficult. Not to physically challenging but very skechy.... Steep drop offs on both sides of the trials.. You usually have to figure out when to head back cause it goes on for ever.. And.. Oh yea make sure you bring enough food and water.. sorry J.. ;)

top of wilhelmina is a nutts one. I think there are 3 summits before hitting the top that overlooks waimanalo and most people turn around at the first one. Good view of diamond head...Anyway I think it's called Ma'umae trail and it's the most challenging trail I 've conquered.

I haven't gone on the Wilhelmina hike, but from what everybody says it sounds like a good one. The most challenging hike I've done is Stairway to Heaven...it just seems to go up forever, but definitely worth the view.