Ugh, the 100 kill challenges. x.x
Those things were monotonous endurance tests more than anything else. I loved the look and atmosphere of Genji, but I really hated those challenges, moreso in Hard mode (where you don't level up or get new gear except the rewards from those challenges, so you pretty much have to do them to do any reasonable amount of damage later on).
That guy certainly makes it look easy, though. Very clean execution. Odd that his best previous score was only in the mid-50's. Wonder what timing he was messing up.