The most difficult task in all of sports?

ESPN doesn't have the greatest tennis coverage, but their summary of Rafael Nadal's win at the 2014 French open posed an interesting question: is beating Nadal at Roland Garros the most difficult task in all of sports right now?

It's an interesting question because it's so open, but to recap, at the time of writing, Nadal has
* a 66-1 record at the French Open (98.5% wins)
* a 90-1 record in 5-set clay-court matches (98.9% wins)
* won the most men's titles at a single slam (9 at the French), beating the runners up (Sampras and Federer with 7 Wimbledon titles each) by 2 titles
* won the French Open the most consecutive times (5) of anyone one the men's tour as well as being tied for the second most consecutive titles (4, tied with Bjorn Borg) 
* won the French Open 9 times out of the 10 years that he's competed in it

And this was the year that he was supposed to be vulnerable; not winning at the Masters events in Monte Carlo, Barcelona and Rome was widely considered a sign of weakness.  In the end though, it doesn't matter if you're a Nadal fan (or even a tennis fan) or not, this is--quite simply--a mind-blowing feat of athletic dominance.  How many other athletes can lay claim to being only 1.5% away from winning every single time that they've competed in a given event over a 10-year period?

So to return to the original question, is beating Nadal at the French Opem the most difficult task in all of sports?  In the current era?  Ever?  Personally, I'm at a bit of a loss to come up with anything that's quite as impressive at the moment, but it's obviously a subjective question that demands a subjective answer, so I'd love to hear your responses!