to all you who did 100%

I really want to get 100% completion. But i am worried that i'm simply not good enough to do it. I know i would eventually get there but i get so frustrated dying that i think i would stop playing the game after a while. I'm not worried about the gambler challenge for instance, i'm quite patient. I'm mostly worried about the challenges involving shooting etc..

What challenges did you find hardest, not most boring but hardest to actually do without dying or miserably fail?