But I beat 7 of them alone!
In the beginning the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move.
Either timed Griffonrook run (non timed is easy), the biggest bg one (eternal i think?) and the one that's in a laboratory with the platforms that you hit a button and they come up and then disappear after a few seconds and you have to keep moving, it's an asura one... I can't remember the name though, that one took me ages first time. Sorry, I'm bad with names, haven't done any jumping puzzles in a long time, I miss them. Even the hard ones were fun (and frustrating)
Griffonrook run with the bomb is the only thing to ever make me never want to never try it again, and I'm pretty OCD about finishing things at least once to say I did it. But I said fuck the bomb, got the achievement, and I'll never try it with the bomb anymore. The griffons are totally fucking random and if they don't reset it messes you up so you gotta wait to be sure. It's just another one of hurr durr what ANet thinks difficulty should be, pure frustration and buggy mechanics. The actual JUMPING part, is of course easy.
Griffon w/bomb was the most annoying.
In the WvW ones I always bring a greatsword and focus and hide behind ledges and stuff and pull people down while they jump.