I just got this achievement using FrozenImplosion's guide. A helpful tip: I found that if you stay at the left side of the screen and wait until the npc walks past you and turns back around facing right, that is exactly when you want to do a head bite because you will scare the npc and he will be stuck in the bottom left of the screen long enough so that you when you head bite the npc you are on, you only have to hold left to make sure you fall back on the next enemy's head. This eliminates having to worry about landing. You have to be very careful to make sure he walks completely past you so that when he turns around he isn't past you, otherwise you won't scare him and have to hit the jump to proceed. Once I figured this out, I got the achievement with relative ease. Hope this helps.